This indicates detection of Linux backdoor used in Freenode IRC network.
Backdoor trojans have the capability to connect to remote hosts and perform actions against the compromised system.
Any unprotected Linux system running the vulnerable version of the IRC server is vulnerable to the attack.
System Compromise: Remote attackers can gain control of vulnerable systems.
This signature's action can be set to "Block" to block this traffic.
Use Anti-Virus software to scan and clean the system.