Unusual traffic

While it is difficult to anticipate what methods a hacker may use in an attempt to infiltrate a network or host, there are a few things that should probably never happen on a normal, healthy network. Due to their usefulness in testing and conveying error conditions, ICMP packets are a likely target for malicious redirection. Since TCP is the predominant transport protocol in use for most applications, you should look out for abnormalities in TCP headers or payloads that could be a sign of malicious intent.

Some examples of abnormalities to look out for are discussed in the following table: