Why attacker install irc after hacking?

["Monty Ree" <chulmin2 () hotmail com>]

Hello, all.

I have operated linux server for a long time.
and I have found that some irc(psybnc etc) related program was installed 
after scan or hacking.

I can't understand 
Why attackers installed and executed irc program?
Why attackers use irc after hacking?
Just chatting is not...I guess..


Thanks in advance.

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