UDP flood UDP Port Denial-of-Service Attack

https://baike.baidu.com/item/UDP%20flood/5504851

UDPFlood是日渐猖厥的流量型DoS攻击，原理也很简单。常见的情况是利用大量UDP小包冲击DNS服务器或Radius认证服务器、流媒体视频服务器。100k bps的UDPFlood经常将线路上的骨干设备例如防火墙打瘫，造成整个网段的瘫痪。由于UDP协议是一种无连接的服务，在UDPFLOOD攻击中，攻击者可发送大量伪造源IP地址的小UDP包。但是，由于UDP协议是无连接性的，所以只要开了一个UDP的端口提供相关服务的话，那么就可针对相关的服务进行攻击。

正常应用情况下，UDP包双向流量会基本相等，而且大小和内容都是随机的，变化很大。出现UDPFlood的情况下，针对同一目标IP的UDP包在一侧大量出现，并且内容和大小都比较固定。

主要防护

编辑

UDP协议与TCP协议不同，是无连接状态的协议，并且UDP应用协议五花八门，差异极大，因此针对UDPFlood的防护非常困难。其防护要根据具体情况对待：

判断包大小，如果是大包攻击则使用防止UDP碎片方法：根据攻击包大小设定包碎片重组大小，通常不小于1500。在极端情况下，可以考虑丢弃所有UDP碎片。

攻击端口为业务端口：根据该业务UDP最大包长设置UDP最大包大小以过滤异常流量。

攻击端口为非业务端口：一个是丢弃所有UDP包，可能会误伤正常业务；一个是建立UDP连接规则，要求所有去往该端口的UDP包，必须首先与TCP端口建立TCP连接。不过这种方法需要很专业的防火墙或其他防护设备支持。

UDP攻击是一种消耗对方资源，同时也消耗攻击者本身的资源的攻击方式，已经没人使用这种过时的东西了。说白了这种攻击方式仅仅就是拼资源而已，看谁的带宽大，看谁能坚持到最后，这种攻击方式没有技术含量，引用别人的话，不要以为洪水无所不能，攻击程序在消耗对方资源同时也在消耗攻击者的资源

https://en.wikipedia.org/wiki/UDP_flood_attack

https://resources.sei.cmu.edu/asset_files/WhitePaper/1996_019_001_496172.pdf#page=5

A UDP flood attack is a volumetric denial-of-service (DoS) attack using the User Datagram Protocol (UDP), a sessionless/connectionless computer networking protocol.

Using UDP for denial-of-service attacks is not as straightforward as with the Transmission Control Protocol (TCP). However, a UDP flood attack can be initiated by sending a large number of UDP packets to random ports on a remote host. As a result, the distant host will:

Check for the application listening at that port;
See that no application listens at that port;
Reply with an ICMP Destination Unreachable packet.

Thus, for a large number of UDP packets, the victimized system will be forced into sending many ICMP packets, eventually leading it to be unreachable by other clients. The attacker(s) may also spoof the IP address of the UDP packets, ensuring that the excessive ICMP return packets do not reach them, and anonymizing their network location(s). Most operating systems mitigate this part of the attack by limiting the rate at which ICMP responses are sent.

UDP Flood Attack Tools:

This attack can be managed by deploying firewalls at key points in a network to filter out unwanted network traffic. The potential victim never receives and never responds to the malicious UDP packets because the firewall stops them. However, as firewalls are 'stateful' i.e. can only hold a number of sessions, firewalls can also be susceptible to flood attacks.