If you have a firewall in the network , it can give you some information.
Try to implement the following to prevent W32.ircbot from spreading in the network
· Use a firewall to block all incoming connections from the Internet to services that should not be publicly available.
· Enforce a Complex password policy..
· Disable AutoPlay to prevent the automatic launching of executable files on network and removable drives, and disconnect the drives when not required. If write access is not required, enable read-only mode if the option is available.
· Turn off file sharing if not needed. If file sharing is required, use ACLs and password protection to limit access. Disable anonymous access to shared folders. Grant access only to user accounts with strong passwords to folders that must be shared.
· Turn off and remove unnecessary services. By default, many operating systems install auxiliary services that are not critical. These services are avenues of attack. If they are removed, threats have less avenues of attack.
· Install all Security patches from Microsoft