wazuh hips规则引擎和ossec的差异分析——本质上语法层面和ossec没有变化，但是公共字段提取出来了，同时正则匹配数据提取灵活性更强

https://documentation.wazuh.com/current/user-manual/ruleset/ruleset-xml-syntax/rules.html  因为是继承自ossec，所以我们从其官方文档里看二者的差异。

 

Rules Syntax

The Wazuh Ruleset combined with any customs rules is used to analyze incoming events and generate alerts when appropriate. The Ruleset is in constant expansion and enhancement thanks to the collaborative effort of our developers and our growing community.

Our aim is to provide the best guidance possible for anyone who may be looking into developing their own custom rules. Remember that you can always contribute to our community.

Overview

The xml labels used to configure rules are listed here.

Option	Values	Description
rule	See table below.	Its starts a new rule and its defining options.
match	Any regular expression.	It will attempt to find a match in the log using sregex by default, deciding if the rule should be triggered.
regex	Any regular expression.	It does the same as match, but with regex as default.
decoded_as	Any decoder's name.	It will match with logs that have been decoded by a specific decoder.
category	Any type.	It will match with logs whose decoder's type concur.
field	Name and any regular expression.	It will compare a field extracted by the decoder in order with a regular expression. ==》匹配更加灵活了，举个例子： <rule id="184737" level="0"> <if_sid>184736</if_sid> <field name="sysmon.parentImage">services.exe|svchost.exe</field> <description>Sysmon - Legitimate Parent Image - taskhost.exe</description> </rule> 也就是说最常用的字段，他提取出来了，用于规则里直接去匹配。
srcip	Any IP address.	It will compare the IP address with the IP decoded as srcip. Use "!" to negate it.
dstip	Any IP address.	It will compare the IP address with the IP decoded as dstip. Use "!" to negate it.
srcport	Any regular expression.	It will compare a regular expression representing a port with a value decoded as srcport.
dstport	Any regular expression.	It will compare a regular expression representing a port with a value decoded as dstport.
data	Any regular expression.	It will compare a regular expression representing a data with a value decoded as data.
extra_data	Any regular expression.	It will compare a regular expression representing an extra data with a value decoded as extra_data.
user	Any regular expression.	It will compare a regular expression representing a user with a value decoded as user.
system_name	Any regular expression.	It will compare a regular expression representing a system name with a value decoded as system_name.
program_name	Any regular expression.	It will compare a regular expression representing a program name with a value pre-decoded as program_name.
protocol	Any regular expression.	It will compare a regular expression representing a protocol with a value decoded as protocol.
hostname	Any regular expression.	It will compare a regular expression representing a hostname with a value pre-decoded as hostname.
time	Any time range. e.g. (hh:mm-hh:mm)	It checks if the event was generated during that time range.
weekday	monday - sunday, weekdays, weekends	It checks whether the event was generated during certain weekdays.
id	Any regular expression.	It will compare a regular expression representing an ID with a value decoded as id
url	Any regular expression.	It will compare a regular expression representing a URL with a value decoded as url
location	Any regular expression.	It will compare a regular expression representing a location with a value pre-decoded as location.
action	Any String or regular expression.	It will compare a string or regular expression representing an action with a value decoded as action.
status	Any regular expression.	It will compare a regular expression representing a status with a value decoded as status.
srcgeoip	Any regular expression.	It will compare a regular expression representing a GeoIP source with a value decoded as srcgeoip.
dstgeoip	Any regular expression.	It will compare a regular expression representing a GeoIP destination with a value decoded as dstgeoip.
if_sid	A list of rule IDs separated by commas or spaces.	It works similar to parent decoder. It will match when a rule ID on the list has previously matched.
if_group	Any group name.	It will match if the indicated group has matched before.
if_level	Any level from 1 to 16.	It will match if that level has already been triggered by another rule.
if_matched_sid	Any rule ID (Number).	Similar to if_sid but it will only match if the ID has been triggered in a period of time.
if_matched_group	Any group name.	Similar to if_group but it will only match if the group has been triggered in a period of time.
same_id	None.	The decoded id must be the same.
different_id	None.	The decoded id must be different.
same_srcip	None.	The decoded srcip must be the same.
different_srcip	None.	The decoded srcip must be different.
same_dstip	None.	The decoded dstip must be the same.
different_dstip	None.	The decoded dstip must be different.
same_srcport	None.	The decoded srcport must be the same.
different_srcport	None.	The decoded srcport must be different.
same_dstport	None.	The decoded dstport must be the same.
different_dstport	None.	The decoded dstport must be different.
same_location	None.	The location must be the same.
different_location	None.	The location must be different.
same_srcuser	None.	The decoded srcuser must be the same.
different_srcuser	None.	The decoded srcuser must be different.
same_user	None.	The decoded user must be the same.
different_user	None.	The decoded user must be different.
not_same_agent	None.	The decoded agent must be different.
same_field	None.	The decoded field must be the same as the previous ones.
different_field	None.	The decoded field must be different than the previous ones.
same_protocol	None.	The decoded protocol must be the same.
different_protocol	None.	The decoded protocol must be different.
same_action	None.	The decoded action must be the same.
different_action	None.	The decoded action must be different.
same_data	None.	The decoded data must be the same.
different_data	None.	The decoded data must be different.
same_extra_data	None.	The decoded extra_data must be the same.
different_extra_data	None.	The decoded extra_data must be different.
same_status	None.	The decoded status must be the same.
different_status	None.	The decoded status must be different.
same_system_name	None.	The decoded system_name must be the same.
different_system_name	None.	The decoded system_name must be different.
same_url	None.	The decoded url must be the same.
different_url	None.	The decoded url must be different.
same_srcgeoip	None.	The decoded srcgeoip must the same.
different_srcgeoip	None.	The decoded srcgeoip must be different.
same_dstgeoip	None.	The decoded dstgeoip must the same.
different_dstgeoip	None.	The decoded dstgeoip must be different.
description	Any String.	Provides a human-readable description to explain what is the purpose of the rule. Please, use this field when creating custom rules.
list	Path to the CDB file.	Perform a CDB lookup using an ossec list.
info	Any String.	Extra information using certain attributes.
options	See the table below.	Additional rule options that can be used.
check_diff	None.	Determines when the output of a command changes.
group	Any String.	Add additional groups to the alert.
mitre	See Mitre table below.	Contains Mitre Technique IDs that fit the rule ==》如前面所说，加入了mitre。
var	Name for the variable. Most used: BAD_WORDS	Defines a variable that can be used anywhere inside the same file.

rule

<rule> is the label that starts the block that defines a rule. In this section, different options for this label are explained.

level	Definition	Specifies the level of the rule. Alerts and responses use this value.
	Allowed values	0 to 16
id	Definition	Specifies the ID of the rule.
	Allowed values	Any number from 1 to 999999
maxsize	Definition	Specifies the maximum size of the event.
	Allowed values	Any number from 1 to 9999
frequency	Definition	Number of times the rule must have matched before firing.
	Allowed values	Any number from 2 to 9999
timeframe	Definition	The timeframe in seconds. This option is intended to be used with the frequency option.
	Allowed values	Any number from 1 to 99999
ignore	Definition	The time (in seconds) to ignore this rule after firing it (to avoid floods).
	Allowed values	Any number from 1 to 999999
overwrite	Definition	Used to supersede a rule with local changes. To maintain consistency between loaded rules, if_sid, if_group, if_level, if_matched_sid, and if_matched_group labels are not taken into account when overwriting a rule. If any of these are encountered, the original value prevails.
	Allowed values	yes, no
noalert	Definition	Not trigger an alert if the rule matches.
	Allowed values	0 (alerts, value by default) or 1 (no alerts). If noalert is set to 1, the event continues analyzing other rules despite the rule matches.

Example:

<rule id="3151" level="10" frequency="8" timeframe="120">
  <if_matched_sid>3102</if_matched_sid>
  <same_source_ip />
  <description>sendmail: Sender domain has bogus MX record. </description>
  <description>It should not be sending e-mail.</description>
  <mitre>
    <id>T1114</id>
    <id>T1499</id>
  </mitre>
  <group>multiple_spam,pci_dss_11.4,gdpr_IV_35.7.d,nist_800_53_SI.4,tsc_CC6.1,tsc_CC6.8,tsc_CC7.2,tsc_CC7.3,</group>
</rule>

The rule is created with ID: 3151 and it will trigger a level 10 alert if the rule 3102 has matched 8 times in the last 120 seconds.

match

Used as a requisite to trigger the rule. It will search for a match in the log event.

Default Value	n/a
Allowed values	Any regex, sregex or pcre2 expression.

Example:

<rule id="100001" maxsize="300" level="3">
  <if_sid>100200</if_sid>
  <match>Queue flood!</match>
  <description>Flooded events queue.</description>
</rule>

If the rule matches the id 100200 and the log contains the Queue flood! phrase in it, rule activates and triggers a level 3 alert.

The attributes below are optional.

Attribute	Description	Value range	Default value
negate	allows to negate the regular expression	no	no
		yes
type	allows to set regular expression type	osmatch	osmatch
		osregex
		pcre2

If match label is declared multiple times within the rule, the following rules apply:

• The resulting value is their concatenation.

• The resulting value of an attribute corresponds to the one specified in the last label. If it is not specified, the default value will be used.

regex

Used as a requisite to trigger the rule. It will search for a match in the log event.

Default Value	n/a
Allowed values	Any regex, sregex or pcre2 expression.

Example:

<rule id="100001" level="3">
  <if_sid>100500</if_sid>
  <regex>\d+.\d+.\d+.\d+</regex>
  <description>Matches any valid IP</description>
</rule>

If the rule matches the ìd 100500 and the event contains any valid IP, the rule is triggered and generates a level 3 alert.

The attributes below are optional.

Attribute	Description	Value range	Default value
negate	allows to negate the regular expression	no	no
		yes
type	allows to set regular expression type	osregex	osregex
		osmatch
		pcre2

If regex label is declared multiple times within the rule, the following rules apply:

• The resulting value is their concatenation.

• The resulting value of an attribute corresponds to the one specified in the last label. If it is not specified, the default value will be used.

decoded_as

Used as a requisite to trigger the rule. It will be triggered if the event has been decoded by a certain decoder. Useful to group rules and have child rules inheriting from it.

Default Value	n/a
Allowed values	Any decoder name

Example:

<rule id="53500" level="0">
  <decoded_as>smtpd</decoded_as>
  <description>OpenSMTPd grouping.</description>
</rule>

The rule will be triggered if the event was decoded by the smtpd decoder. Now is possible to make more rules that will inherit from this one, specifically made for OpenSMTPd events.

category

Used as a requisite to trigger the rule. It will be triggered if the decoder included that log in said category.

Default Value	n/a
Allowed values	Any type

Example:

<rule id="01" level="0" noalert="1">
  <category>syslog</category>
  <description>Generic template for all syslog rules.</description>
</rule>

The rule will be triggered if the event has previously been cataloged syslog by the decoder, but it will not trigger an alert. Instead, it will be matched by other rules that might trigger alerts if needed.

field

Used as a requisite to trigger the rule. It will check for a match in the content of a field extracted by the decoder.

Default Value	n/a
Allowed values	Any regex, sregex or pcre2 expression.

Below is the list of attributes.

Attribute	Description	Value range	Default value
name	specifies the name of the field extracted by the decoder.	n/a	n/a
negate	allows to negate the regular expression	no	no
		yes
type	allows to set regular expression type	osregex	osregex
		osmatch
		pcre2

Example:

<rule id="87100" level="0">
    <decoded_as>json</decoded_as>
    <field name="integration">virustotal</field>
    <description>VirusTotal integration messages.</description>
    <options>no_full_log</options>
</rule>

This rule, groups events decoded from json that belong to an integration called VirusTotal. It checks the field decoded as integration and if its content is virustotal the rule is triggered.

srcip

Used as a requisite to trigger the rule. It will compare any IP address or CIDR block to an IP decoded as srcip. Use "!" to negate it.

Default Value	n/a
Allowed values	Any srcip

Example:

<rule id="100105" level="8">
    <if_sid>100100</if_sid>
    <srcip>10.25.23.12</srcip>
    <description>Forbidden srcip has been detected.</description> ==》这种用于黑白名单的匹配还是好用的！！！
</rule>

This rule will trigger when that exact scrip has been decoded.

The attributes below are optional.

Attribute	Description	Value range	Default value
negate	allows to negate the regular expression	no	no
		yes

If srcip label is declared multiple times within the rule, the following rules apply:

• The resulting value is their concatenation.

• The resulting value of an attribute corresponds to the one specified in the last label. If it is not specified, the default value will be used.

dstip

Used as a requisite to trigger the rule. It will compare any IP address or CIDR block to an IP decoded as dstip. Use "!" to negate it.

Default Value	n/a
Allowed values	Any dstip

Example:

<rule id="100110" level="5">
    <if_sid>100100</if_sid>
    <dstip>!198.168.41.30</dstip>
    <description>A different dstip has been detected.</description>
</rule>

This rule will trigger when an dstip different from 198.168.41.30 is detected.

The attributes below are optional.

Attribute	Description	Value range	Default value
negate	allows to negate the regular expression	no	no
		yes

If dstip label is declared multiple times within the rule, the following rules apply:

• The resulting value is their concatenation.

• The resulting value of an attribute corresponds to the one specified in the last label. If it is not specified, the default value will be used.

srcport

Used as a requisite to trigger the rule. It will check the source port (decoded as srcport).

Default Value	n/a
Allowed values	Any regex, sregex or pcre2 expression.

Example:

<rule id="100110" level="5">
    <if_sid>100100</if_sid>
    <srcport type="pcre2">^5000[0-7]$</srcport>
    <description>Source port $(srcport) is detected.</description>
</rule>

This rule will trigger when srcport is in the range of 50000 to 50007.

The attributes below are optional.

Attribute	Description	Value range	Default value
negate	allows to negate the regular expression	no	no
		yes
type	allows to set regular expression type	osmatch	osmatch
		osregex
		pcre2

If srcport label is declared multiple times within the rule, the following rules apply:

• The resulting value is their concatenation.

• The resulting value of an attribute corresponds to the one specified in the last label. If it is not specified, the default value will be used.

dstport

Used as a requisite to trigger the rule. It will check the destination port (decoded as dstport).

Default Value	n/a
Allowed values	Any regex, sregex or pcre2 expression.

The attributes below are optional.

Attribute	Description	Value range	Default value
negate	allows to negate the regular expression	no	no
		yes
type	allows to set regular expression type	osmatch	osmatch
		osregex
		pcre2

If dstport label is declared multiple times within the rule, the following rules apply:

• The resulting value is their concatenation.

• The resulting value of an attribute corresponds to the one specified in the last label. If it is not specified, the default value will be used.

data

Used as a requisite to trigger the rule. It will check the data (decoded as data).

Default Value	n/a
Allowed values	Any regex, sregex or pcre2 expression.

The attributes below are optional.

Attribute	Description	Value range	Default value
negate	allows to negate the regular expression	no	no
		yes
type	allows to set regular expression type	osmatch	osmatch
		osregex
		pcre2

If data label is declared multiple times within the rule, the following rules apply:

• The resulting value is their concatenation.

• The resulting value of an attribute corresponds to the one specified in the last label. If it is not specified, the default value will be used.

extra_data

Used as a requisite to trigger the rule. It will compare any string with the one decoded into the extra_data field.

Default Value	n/a
Allowed values	Any regex, sregex or pcre2 expression.==》提取的时候可以标记下，最后在写规则的时候用于正则匹配！

Example:

<rule id="7301" level="0">
  <category>windows</category>
  <extra_data>^Symantec AntiVirus</extra_data>
  <description>Grouping of Symantec AV rules from eventlog.</description>
</rule>

This rule will trigger when the log belongs to windows category and the decoded field extra_data is: Symantec AntiVirus

The attributes below are optional.

Attribute	Description	Value range	Default value
negate	allows to negate the regular expression	no	no
		yes
type	allows to set regular expression type	osmatch	osmatch
		osregex
		pcre2

If extra_data label is declared multiple times within the rule, the following rules apply:

• The resulting value is their concatenation.

• The resulting value of an attribute corresponds to the one specified in the last label. If it is not specified, the default value will be used.

user

Used as a requisite to trigger the rule. It will check the username (decoded as user).

Default Value	n/a
Allowed values	Any regex, sregex or pcre2 expression.

Example:

<rule id="140101" level="12">
  <if_group>authentication_success</if_group>
  <user negate="yes">wazuh|root</user>
  <description>Unexpected user successfully logged to the system.</description>
</rule>

This rule will trigger when a user different from root or wazuh successfully login into the system.

The attributes below are optional.

Attribute	Description	Value range	Default value
negate	allows to negate the regular expression	no	no
		yes
type	allows to set regular expression type	osmatch	osmatch
		osregex
		pcre2

If user label is declared multiple times within the rule, the following rules apply:

• The resulting value is their concatenation.

• The resulting value of an attribute corresponds to the one specified in the last label. If it is not specified, the default value will be used.

system_name

Used as a requisite to trigger the rule. It will check the system name (decoded as system_name).

Default Value	n/a
Allowed values	Any regex, sregex or pcre2 expression.

The attributes below are optional.

Attribute	Description	Value range	Default value
negate	allows to negate the regular expression	no	no
		yes
type	allows to set regular expression type	osmatch	osmatch
		osregex
		pcre2

If system_name label is declared multiple times within the rule, the following rules apply:

• The resulting value is their concatenation.

• The resulting value of an attribute corresponds to the one specified in the last label. If it is not specified, the default value will be used.

program_name

Used as a requisite to trigger the rule. The program's name is decoded from syslog process name.

Default Value	n/a
Allowed values	Any regex, sregex or pcre2 expression.

Example:

<rule id="1005" level="5">
  <program_name>syslogd</program_name>
  <match>^restart</match>
  <description>Syslogd restarted.</description>
  <group>pci_dss_10.6.1,gpg13_10.1,gpg13_4.14,gdpr_IV_35.7.d,hipaa_164.312.b,nist_800_53_AU.6,</group>
</rule>

The rule will trigger when the program Syslogd restarted.

The attributes below are optional.

Attribute	Description	Value range	Default value
negate	allows to negate the regular expression	no	no
		yes
type	allows to set regular expression type	osmatch	osmatch
		osregex
		pcre2

If program_name label is declared multiple times within the rule, the following rules apply:

• The resulting value is their concatenation.

• The resulting value of an attribute corresponds to the one specified in the last label. If it is not specified, the default value will be used.

protocol

Used as a requisite to trigger the rule. It will check the protocol (decoded as protocol).

Default Value	n/a
Allowed values	Any regex, sregex or pcre2 expression.

The attributes below are optional.

Attribute	Description	Value range	Default value
negate	allows to negate the regular expression	no	no
		yes
type	allows to set regular expression type	osmatch	osmatch
		osregex
		pcre2

If protocol label is declared multiple times within the rule, the following rules apply:

• The resulting value is their concatenation.

• The resulting value of an attribute corresponds to the one specified in the last label. If it is not specified, the default value will be used.

hostname

Used as a requisite to trigger the rule. Any hostname (decoded as the syslog hostname) or log file.

Default Value	n/a
Allowed values	Any regex, sregex or pcre2 expression.

Example:

<rule id="2931" level="0">
  <hostname>yum.log$</hostname>
  <match>^Installed|^Updated|^Erased</match>
  <description>Yum logs.</description>
</rule>

This rule will group rules for Yum logs when something is either being installed, updated or erased.

The attributes below are optional.

Attribute	Description	Value range	Default value
negate	allows to negate the regular expression	no	no
		yes
type	allows to set regular expression type	osmatch	osmatch
		osregex
		pcre2

If hostname label is declared multiple times within the rule, the following rules apply:

• The resulting value is their concatenation.

• The resulting value of an attribute corresponds to the one specified in the last label. If it is not specified, the default value will be used.

time

Used as a requisite to trigger the rule. Used for checking the time that the event was generated.

Default Value	n/a
Allowed values	Any time range (hh:mm-hh:mm, hh:mm am-hh:mm pm, hh-hh, hh am-hh pm)

Example:

<rule id="17101" level="9">
  <if_group>authentication_success</if_group>
  <time>6 pm - 8:30 am</time>
  <description>Successful login during non-business hours.</description>
  <group>login_time,pci_dss_10.2.5,pci_dss_10.6.1,gpg13_7.1,gpg13_7.2,gdpr_IV_35.7.d,gdpr_IV_32.2,hipaa_164.312.b,nist_800_53_AU.14,nist_800_53_AC.7,nist_800_53_AU.6,</group>
</rule>

This rule will trigger when there is a successful login between 6 pm and 8 am.

weekday

Used as a requisite to trigger the rule. Checks the weekday that the event was generated.

Default Value	n/a
Allowed values	monday - sunday, weekdays, weekends

Example:

<rule id="17102" level="9">
  <if_group>authentication_success</if_group>
  <weekday>weekends</weekday>
  <description>Successful login during weekend.</description>
  <group>login_day,pci_dss_10.2.5,pci_dss_10.6.1,gpg13_7.1,gpg13_7.2,gdpr_IV_35.7.d,gdpr_IV_32.2,hipaa_164.312.b,nist_800_53_AU.14,nist_800_53_AC.7,nist_800_53_AU.6,</group>
</rule>

This rule will trigger when there is a successful login during the weekend.

id

Used as a requisite to trigger the rule. It will check any ID (decoded as the ID).

Default Value	n/a
Allowed values	Any regex, sregex or pcre2 expression.

Example:

<rule id="81100" level="0">
    <decoded_as>kernel</decoded_as>
    <id>usb</id>
    <description>USB messages grouped.</description>
</rule>

This rule will group the logs whose decoded ID is usb.

The attributes below are optional.

Attribute	Description	Value range	Default value
negate	allows to negate the regular expression	no	no
		yes
type	allows to set regular expression type	osmatch	osmatch
		osregex
		pcre2

If id label is declared multiple times within the rule, the following rules apply:

• The resulting value is their concatenation.

• The resulting value of an attribute corresponds to the one specified in the last label. If it is not specified, the default value will be used.

url

Used as a requisite to trigger the rule. It will check any URL (decoded as the URL).

Default Value	n/a
Allowed values	Any regex, sregex or pcre2 expression.

Example:

<rule id="31102" level="0">
  <if_sid>31101</if_sid>
  <url>.jpg$|.gif$|favicon.ico$|.png$|robots.txt$|.css$|.js$|.jpeg$</url>
  <compiled_rule>is_simple_http_request</compiled_rule>
  <description>Ignored extensions on 400 error codes.</description>
</rule>

This rule is a child from a level 5 rule 31101 and becomes a level 0 rule when it confirms that the extensions are nothing to worry about.

The attributes below are optional.

Attribute	Description	Value range	Default value
negate	allows to negate the regular expression	no	no
		yes
type	allows to set regular expression type	osmatch	osmatch
		osregex
		pcre2

If url label is declared multiple times within the rule, the following rules apply:

• The resulting value is their concatenation.

• The resulting value of an attribute corresponds to the one specified in the last label. If it is not specified, the default value will be used.

location

Used as a requisite to trigger the rule. It will check the content of the field location and trying to find a match.

Default Value	n/a
Allowed values	Any regex, sregex or pcre2 expression.

The location identifies the origin of the input. If the event comes from an agent, its name and registered IP address (as it was added) is appended to the location.

Example of a location for a log pulled from "/var/log/syslog" in an agent with name "dbserver" and registered with IP "any":

 

(dbserver) any->/var/log/syslog

The following components use a static location:

Component	Location
Windows Eventchannel	EventChannel
Windows Eventlog	WinEvtLog
FIM (Syscheck)	syscheck
Rootcheck	rootcheck
Syscollector	syscollector
Vuln Detector	vulnerability-detector
Azure Logs	azure-logs
AWS S3 integration	aws-s3
Docker integration	Wazuh-Docker
Osquery integration	osquery
OpenSCAP integration	open-scap
CIS-CAT integration	wodle_cis-cat
SCA module	sca

Example:

<rule id="24000" level="3">
  <location>osquery$</location>
  <description>osquery message</description>
</rule>

This rule, groups logs that come from osquery location. Triggering a level 3 alert for it.

The attributes below are optional.

Attribute	Description	Value range	Default value
negate	allows to negate the regular expression	no	no
		yes
type	allows to set regular expression type	osmatch	osmatch
		osregex
		pcre2

If location label is declared multiple times within the rule, the following rules apply:

• The resulting value is their concatenation.

• The resulting value of an attribute corresponds to the one specified in the last label. If it is not specified, the default value will be used.

action

Used as a requisite to trigger the rule. It will check any action (decoded as the ACTION).

Default Value	n/a
Allowed values	Any regex, sregex or pcre2 expression.

Example:

<rule id="4502" level="4">
  <if_sid>4500</if_sid>
  <action type="osregex">warning|WARN</action>
  <description>Netscreen warning message.</description>
</rule>

This rule will trigger a level 4 alert when the decoded action from Netscreen is warning or WARN.

The attributes below are optional.

Attribute	Description	Value range	Default value
negate	allows to negate the regular expression	no	no
		yes
type	allows to set regular expression type	osmatch	string
		osregex
		pcre2

Note

Use type attribute only for regular expression match. It must be omitted if action field try to match a string.

If action label is declared multiple times within the rule, the following rules apply:

• The resulting value is their concatenation.

• The resulting value of an attribute corresponds to the one specified in the last label. If it is not specified, the default value will be used.

status

Checks the actual status of an event.

Default Value	n/a
Allowed values	Any regex, sregex or pcre2 expression.

Example:

<rule id="213" level="7">
  <if_sid>210</if_sid>
  <status>aborted</status>
  <description>Remote upgrade could not be launched. Error: $(error).</description>
  <group>upgrade,upgrade_failure,</group>
</rule>

The attributes below are optional.

Attribute	Description	Value range	Default value
negate	allows to negate the regular expression	no	no
		yes
type	allows to set regular expression type	osmatch	osmatch
		osregex
		pcre2

If status label is declared multiple times within the rule, the following rules apply:

• The resulting value is their concatenation.

• The resulting value of an attribute corresponds to the one specified in the last label. If it is not specified, the default value will be used.

srcgeoip

Used as a requisite to trigger the rule. It will check the GeoIP source (decoded as srcgeoip).

Default Value	n/a
Allowed values	Any regex, sregex or pcre2 expression.

The attributes below are optional.

Attribute	Description	Value range	Default value
negate	allows to negate the regular expression	no	no
		yes
type	allows to set regular expression type	osmatch	osmatch
		osregex
		pcre2

If srcgeoip label is declared multiple times within the rule, the following rules apply:

• The resulting value is their concatenation.

• The resulting value of an attribute corresponds to the one specified in the last label. If it is not specified, the default value will be used.

dstgeoip

Used as a requisite to trigger the rule. It will check the GeoIP destination (decoded as dstgeoip).

Default Value	n/a
Allowed values	Any regex, sregex or pcre2 expression.

The attributes below are optional.

Attribute	Description	Value range	Default value
negate	allows to negate the regular expression	no	no
		yes
type	allows to set regular expression type	osmatch	osmatch
		osregex
		pcre2

If dstgeoip label is declared multiple times within the rule, the following rules apply:

• The resulting value is their concatenation.

• The resulting value of an attribute corresponds to the one specified in the last label. If it is not specified, the default value will be used.

if_sid

Used as a requisite to trigger the rule. Matches when an ID on the list has previously matched. It is similar to a child decoder, with the key difference that alerts can have as many descendants as necessary, whereas decoder cannot have "grandchildren".

Default Value	n/a
Allowed values	Any rule ID. Multiple values must be separated by commas or spaces.

Example:

<rule id="100110" level="5">
  <if_sid>100100, 100101</if_sid>
  <match>Error</match>
  <description>There is an error in the log.</description>
</rule>

The rule 100110 is triggered when either of the parent rules has matched and the logs contain the word "Error".

if_group

Used as a requisite to trigger the rule. Matches if the group has matched before.

Default Value	n/a
Allowed values	Any Group

Example:

<rule id="184676" level="12">
    <if_group>sysmon_event1</if_group>
    <field name="sysmon.image">lsm.exe</field>
    <description>Sysmon - Suspicious Process - lsm.exe</description>
    <group>pci_dss_10.6.1,pci_dss_11.4,gdpr_IV_35.7.d,hipaa_164.312.b,nist_800_53_AU.6,nist_800_53_SI.4,</group>
</rule>

The rule matches if the group sysmon_event1 has previously matched before and if the field decoded as sysmon.image is "lsm.exe".

if_level

Matches if the level has matched before.

Default Value	n/a
Allowed values	Any level from 1 to 16

if_matched_sid

Matches if an alert of the defined ID has been triggered in a set number of seconds.

This option is used in conjunction with frequency and timeframe.

Default Value	n/a
Allowed values	Any rule id

Note

Rules at level 0 are discarded immediately and will not be used with the if_matched_rules. The level must be at least 1, but the <no_log> option can be added to the rule to make sure it does not get logged.

Example:

 

<rule id="30316" level="10" frequency="10" timeframe="120">
  <if_matched_sid>30315</if_matched_sid>
  <same_source_ip />
  <description>Apache: Multiple Invalid URI requests from same source.</description>
  <mitre>
    <id>T1499</id>
  </mitre>
  <group>gdpr_IV_35.7.d,hipaa_164.312.b,invalid_request,nist_800_53_AU.14,nist_800_53_AC.7,nist_800_53_SI.4,pci_dss_10.2.4,pci_dss_11.4,tsc_CC6.1,tsc_CC6.8,tsc_CC7.2,tsc_CC7.3,</group>
</rule>

The rule is triggered when rule 30315 has been triggered 10 times in 120 seconds and if the requests were made by the same srcip.

if_matched_group

Matches if an alert of the defined group has been triggered in a set number of seconds.

This option is used in conjunction with frequency and timeframe.

Default Value	n/a
Allowed values	Any Group

Example:

<rule id="40113" level="12" frequency="8" timeframe="360">
  <if_matched_group>virus</if_matched_group>
  <description>Multiple viruses detected - Possible outbreak.</description>
  <group>virus,pci_dss_5.1,pci_dss_5.2,pci_dss_11.4,gpg13_4.2,gdpr_IV_35.7.d,nist_800_53_SI.3,nist_800_53_SI.4,</group>
</rule>

The rule will trigger when the group virus has been matched 8 times in the last 360 seconds.

if_fts

Makes the decoder that processed the event to take the fts line into consideration.

Example of use

<if_fts />

Note

The dynamic filters same_field or not_same_field will not work with the static fields (user, srcip, dstip, etc.) and the specific ones have to be used instead.

same_id

Specifies that the decoded id must be the same. This option is used in conjunction with frequency and timeframe.

Example of use

<same_id />

different_id

Specifies that the decoded id must be different. This option is used in conjunction with frequency and timeframe.

Example of use

<different_id />

same_srcip

Specifies that the decoded source IP address must be the same. This option is used in conjunction with frequency and timeframe.

Example of use

<same_srcip />

Deprecated label same_source_ip works like an alias for same_srcip.

different_srcip

Specifies that the decoded source IP address must be different. This option is used in conjunction with frequency and timeframe.

Example of use

<different_srcip />

Deprecated label not_same_source_ip works like an alias for different_srcip.

same_dstip

Specifies that the decoded destination IP address must be the same. This option is used in conjunction with frequency and timeframe.

Example of use

<same_dstip />

different_dstip

Specifies that the decoded destination IP address must be different. This option is used in conjunction with frequency and timeframe.

Example of use

<different_dstip />

same_srcport

Specifies that the decoded source port must be the same. This option is used in conjunction with frequency and timeframe.

Example of use

<same_srcport />

different_srcport

Specifies that the decoded source port must be different. This option is used in conjunction with frequency and timeframe.

Example of use

<different_srcport />

same_dstport

Specifies that the decoded destination port must be the same. This option is used in conjunction with frequency and timeframe.

Example of use

<same_dstport />

different_dstport

Specifies that the decoded destination port must be different. This option is used in conjunction with frequency and timeframe.

Example of use

<different_dstport />

same_location

Specifies that the location must be the same. This option is used in conjunction with frequency and timeframe.

Example of use

<same_location />

different_location

Specifies that the decoded location must be different. This option is used in conjunction with frequency and timeframe.

Example of use

<different_location />

same_srcuser

Specifies that the decoded source user must be the same. This option is used in conjunction with frequency and timeframe.

Example of use

<same_srcuser />

different_srcuser

Specifies that the decoded source user must be different. This option is used in conjunction with frequency and timeframe.

Example of use

<different_srcuser />

same_user

Specifies that the decoded user must be the same. This option is used in conjunction with frequency and timeframe.

Example of use

<same_user />

different_user

Specifies that the decoded user must be different. This option is used in conjunction with frequency and timeframe.

Example of use

<different_user />

not_same_agent

Specifies that the decoded agent must be different. This option is used in conjunction with frequency and timeframe.

Example of use

<not_same_agent />

same_field

The value of the dynamic field specified in this option must appear in previous events a frequency number of times within the required timeframe.

Example of use

<same_field>key</same_field>

As an example of this option, check these rules:

 

<!-- {"key":"value", "key2":"AAAA"} -->
<rule id="100001" level="3">
  <decoded_as>json</decoded_as>
  <field name="key">value</field>
  <description>Testing JSON alert</description>
</rule>

<rule id="100002" level="10" frequency="4" timeframe="300">
  <if_matched_sid>100001</if_matched_sid>
  <same_field>key2</same_field>
  <description>Testing same_field option</description>
</rule>

Rule 100002 will fire when key2 in the currently considered event is the same in four events that matched rule 100001 before within the last 300 seconds. Therefore, for the following events sequence:

 

{"key":"value", "key2":"AAAA"}
{"key":"value", "key2":"AAAA"}
{"key":"value", "key2":"BBBB"}
{"key":"value", "key2":"AAAA"}
{"key":"value", "key2":"CCCC"}
{"key":"value", "key2":"CCCC"}
{"key":"value", "key2":"AAAA"}

The last event will fire rule 100002 instead of 100001 because it found the value AAAA in three of the previous events. The corresponding alert looks like this one:

Output

{
  "timestamp": "2020-03-04T03:00:28.973-0800",
  "rule": {
    "level": 10,
    "description": "Testing same_field option",
    "id": "100002",
    "frequency": 4,
    "firedtimes": 1,
    "mail": false,
    "groups": [
      "local"
    ]
  },
  "agent": {
    "id": "000",
    "name": "ubuntu"
  },
  "manager": {
    "name": "ubuntu"
  },
  "id": "1583319628.14426",
  "previous_output": "{\"key\":\"value\",\"key2\":\"AAAA\"}\n{\"key\":\"value\",\"key2\":\"AAAA\"}\n{\"key\":\"value\",\"key2\":\"AAAA\"}",
  "full_log": "{\"key\":\"value\",\"key2\":\"AAAA\"}",
  "decoder": {
    "name": "json"
  },
  "data": {
    "key": "value",
    "key2": "AAAA"
  },
  "location": "/root/test.log"
}

different_field

It is the opposite setting of same_field. The value of the dynamic field specified in this option must be different than the ones found in previous events a frequency number of times within the required timeframe.

Example of use

<different_field>key2</different_field>

global_frequency

Specifies that the events of all agents will be contemplated when using the frequency and timeframe options. By default, only the events generated by the same agent will be taken into account to increase the frequency counter for a rule.

Example of use

<global_frequency />

Warning

Although the label contains the word global, this option works at manager level, not at cluster level.

same_protocol

Specifies that the decoded protocol must be the same. This option is used in conjunction with frequency and timeframe.

Example of use

<same_protocol />

different_protocol

Specifies that the decoded protocol must be different. This option is used in conjunction with frequency and timeframe.

Example of use

<different_protocol />

same_action

Specifies that the decoded action must be the same. This option is used in conjunction with frequency and timeframe.

Example of use

<same_action />

different_action

Specifies that the decoded action must be different. This option is used in conjunction with frequency and timeframe.

Example of use

<different_action />

same_data

Specifies that the decoded data must be the same. This option is used in conjunction with frequency and timeframe.

Example of use

<same_data />

different_data

Specifies that the decoded data must be different. This option is used in conjunction with frequency and timeframe.

Example of use

<different_data />

same_extra_data

Specifies that the decoded extra data must be the same. This option is used in conjunction with frequency and timeframe.

Example of use

<same_extra_data />

different_extra_data

Specifies that the decoded extra data must be different. This option is used in conjunction with frequency and timeframe.

Example of use

<different_extra_data />

same_status

Specifies that the decoded status must be the same. This option is used in conjunction with frequency and timeframe.

Example of use

<same_status />

different_status

Specifies that the decoded status must be different. This option is used in conjunction with frequency and timeframe.

Example of use

<different_status />

same_system_name

Specifies that the decoded system name must be the same. This option is used in conjunction with frequency and timeframe.

Example of use

<same_system_name />

different_system_name

Specifies that the decoded system name must be different. This option is used in conjunction with frequency and timeframe.

Example of use

<different_system_name />

same_url

Specifies that the decoded url must be the same. This option is used in conjunction with frequency and timeframe.

Example of use

<same_url />

different_url

Specifies that the decoded url must be different. This option is used in conjunction with frequency and timeframe.

Example of use

<different_url />

same_srcgeoip

Specifies that the source geoip location must be the same. This option is used in conjunction with frequency and timeframe.

Example of use

<same_srcgeoip />

different_srcgeoip

Specifies that the source geoip location must be different. This option is used in conjunction with frequency and timeframe.

Example of use

<different_srcgeoip />

Example:

As an example of these last options, check this rule:

<rule id=100005 level="0">
  <match> Could not open /home </match>
  <same_user />
  <different_srcgeoip />
  <same_dstport />
</rule>

That rule filters when the same user tries to open file /home but returns an error, on a different ip and using the same port.

same_dstgeoip

Specifies that the destination geoip location must be the same. This option is used in conjunction with frequency and timeframe.

Example of use

<same_dstgeoip />

different_dstgeoip

Specifies that the destination geoip location must be different. This option is used in conjunction with frequency and timeframe.

Example of use

<different_dstgeoip />

description

Specifies a human-readable description to the rule in order to provide context to each alert regarding the nature of the events matched by it.

Default Value	n/a
Allowed values	Any string

Examples:

<rule id="100015" level="2">
  ...
  <description> A timeout occurred. </description>
</rule>

<rule id="100035" level="4">
  ...
  <description> File missing. Root access unrestricted. </description>
</rule>

Since Wazuh version 3.3 it is possible to include any decoded field (static or dynamic) to the description message. You can use the following syntax: $(field_name) to add a field to the description.

Example:

<rule id="100005" level="8">
  <match>illegal user|invalid user</match>
  <description>sshd: Attempt to login using a non-existent user from IP $(attempt_ip)</description>
  <options>no_log</options>
</rule>

If description label is declared multiple times within the rule, the following rules apply:

• The resulting value is their concatenation.

list

Perform a CDB lookup using an ossec list. This is a fast on-disk database which will always find keys within two seeks of the file.

Default Value	n/a
Allowed values	Path to the CDB file to be used for lookup from the OSSEC directory. Must also be included in the ossec.conf file.

Attribute	Description
field	key in the CDB: srcip, srcport, dstip, dstport, extra_data, user, url, id, hostname, program_name, status, action, dynamic field.
lookup	match_key	key to search within the cdb and will match if they key is present. Default.
	not_match_key	key to search and will match if it is not present in the database.
	match_key_value	searched for in the cdb. It will be compared with regex from attribute check_value.
	address_match_key	IP address and the key to search within the cdb and will match if they key is present.
	not_address_match_key	IP address and the key to search and will match if it IS NOT present in the database.
	address_match_key_value	IP address to search in the cdb. It will be compared with regex from attribute check_value.
check_value	regex for matching on the value pulled out of the cdb when using types: address_match_key_value, match_key_value

Example:

<rule id="80780" level="3">
    <if_sid>80700</if_sid>
    <list field="audit.key" lookup="match_key_value" check_value="write">etc/lists/audit-keys</list>
    <description>Audit: Watch - Write access</description>
    <group>audit_watch_write,gdpr_IV_30.1.g,</group>
</rule>

The rule will look for "audit.key" in the CDB list. Where it will check if its equal to "write", in which case it will match and trigger a level 3 alert.

info

Extra information may be added through the following attributes:

Default Value	n/a
Allowed values	Any string

Attribute	Allowed values	Description
type	text	This is the default when no type is selected. Additional information about the alert/event.
	link	Link to more information about the alert/event.
	cve	The CVE Number related to this alert/event.
	ovsdb	The osvdb id related to this alert/event.

Example:

<rule id="5714" level="14" timeframe="120" frequency="3">
  <if_matched_sid>5713</if_matched_sid>
  <match>Local: crc32 compensation attack</match>
  <description>sshd: SSH CRC-32 Compensation attack</description>
  <info type="cve">2001-0144</info>
  <info type="link">http://www.securityfocus.com/bid/2347/info/</info>
  <group>exploit_attempt,pci_dss_11.4,pci_dss_6.2,gpg13_4.12,gdpr_IV_35.7.d,nist_800_53_SI.4,nist_800_53_SI.2,</group>
</rule>

The rule provides additional information about the threat it detects.

options

Additional rule options.

Attribute	Description
alert_by_email	Always alert by email.
no_email_alert	Never alert by email.
no_log	Do not log this alert.
no_full_log	Do not include the full_log field in the alert.
no_counter	Omit field rule.firedtimes in the JSON alert.

Example:

<rule id="9800" level="8">
  <match>illegal user|invalid user</match>
  <description>sshd: Attempt to login using a non-existent user</description>
  <options>no_log</options>
</rule>

Note

Use one <options> tag for each option you want to add.

check_diff

Used to determine when the output of a command changes.

Example:

<rule id="534" level="1">
  <if_sid>530</if_sid>
  <match>ossec: output: 'w'</match>
  <check_diff />
  <options>no_log</options>
  <description>List of logged in users. It will not be alerted by default.</description>
</rule>

group

Add additional groups to the alert. Groups are optional tags added to alerts.

They can be used by other rules by using if_group or if_matched_group, or by alert parsing tools to categorize alerts.

Groups are variables that define behavior. When an alert includes that group label, this behavior will occur.

Example:

<rule id="3801" level="4">
  <description>Group for rules related with spam.</description>
  <group>spam,</group>
</rule>

Now, every rule with the line <group>spam,</group> will be included in that group.

It's a very useful label to keep the rules ordered.

Default Value	n/a
Allowed values	Any String

mitre

Specifies the MITRE ATT&CK technique ID or IDs that fit in well with the rule.

Required label	Value
id	MITRE ATT&CK technique ID.

Example:

<rule id="100002" level="10">
  <description>Attack technique sample.</description>
  <mitre>
    <id>T1110</id>
    <id>T1037</id>
  </mitre>
</rule>

var

Defines a variable that may be used in any place of the same file.

Attribute	Value
name	Name for the variable.

Example:

 <var name="joe_folder">/home/joe/</var>

  <group name="local,">

    <rule id="100001" level="5">
      <if_sid>550</if_sid>
      <field name="file">^$joe_folder</field>
      <description>A Joe's file was modified.</description>
      <group>ossec,pci_dss_10.6.1,gpg13_10.1,gdpr_IV_35.7.d,</group>
    </rule>

</group>

BAD_WORDS

<var name="BAD_WORDS">error|warning|failure</var>

BAD_WORDS is a very used use case of the <var> option.

It is used to include many words in the same variable. Later, this variable can be matched into the decoders to check if any of those words are in a caught event.

Example:

<var name="BAD_WORDS">error|warning|failure</var>

<group name="syslog,errors,">
  <rule id="XXXX" level="2">
    <match>$BAD_WORDS</match>
    <description>Error found.</description>
  </rule>
</group>