Intrusion Signature

An intrusion signature is a kind of footprint left behind by perpetrators of a malicious attack on a computer network or system. Each intrusion signature is different, but they may appear in the form of evidence such as records of failed logins, unauthorized software executions, unauthorized file or directory access, or improper use of administrative privileges.

Intrusion signatures are recorded and logged by intrusion detection systems and studied and documented by system administrators who can often configure or modify the system to prevent the same attack from happening again, thus strengthening security against future attacks. System administrators may be able to determine such investigative information about how and when the intrusion was executed and the skill level of the perpetrator.

Most intrusion detection systems use one of the following detections methods:

• Signature-based detection
• Statistical anomaly-based detection
• Stateful protocol analysis detection

By recording and logging intrusion signatures in a database, the signature-based detection method monitors network traffic in search of signature matches. When these are found, the detection system takes the appropriate action.

Two types of intrusion signatures are commonly used

• Exploit based
• Vulnerability based

Intrusion detection systems use the former to analyze patterns previously recorded and protect against repetitions; they use the latter by analyzing vulnerabilities in a program, the program’s executions and the conditions needed to exploit those vulnerabilities.