Explanation: Following are the basic categories of signatures: Informational (benign): These types of signatures trigger on normal network activity. For example: ICMP echo requests The opening or closing of TCP or UDP connections Reconnaissance: These types of signatures trigger on attacks that uncover resources and hosts that are reachable, as well as any possible vulnerabilities that they might contain. For example: Reconnaissance attacks include ping sweeps DNS queries Port scanning Access: These types of signatures trigger on access attacks, which include unauthorized access, unauthorized escalation of privileges, and access to protected or sensitive data. For example:
Back Orifice A Unicode attack against the Microsoft IIS NetBus DoS: These types of signatures trigger on attacks that attempt to reduce the level of a resource or system, or to cause it to crash. For example: TCP SYN floods The Ping of Death Smurf Fraggle Trinoo Tribe Flood Network