What is a Signature?
In general, a signature refers to a "written or digital signature." In the context of programming, a signature refers to the information used to identify a method, such as its name, parameter types, number, order, and return type (definitions may vary depending on the programming language). However, in the context of computer security, a signature refers to the distinctive patterns of malicious activities, such as malware or unauthorized access. Files that aggregate these patterns are called signature files, and the functionality that uses signatures to detect and block attacks is referred to as the signature feature.
Using signatures to defend against attacks typically follows a blacklist approach, where a list of known threats is maintained to block dangerous activities. This provides the advantage of reliably and swiftly responding to known attacks. However, this approach has the limitation of being unable to address unknown attacks or new threats not yet included in the blacklist.
To address this limitation, combining the blacklist approach with a whitelist approach is recommended. With whitelisting, only explicitly permitted activities are allowed. By permitting activity on the whitelist, blocking patterns on the blacklist, and treating everything else as a gray zone requiring verification, a more comprehensive defense strategy can be achieved.
F5’s BIG-IP leverages both blacklist-type signatures for attack patterns and whitelists for legitimate traffic, enabling the detection and prevention of attacks effectively.