Icrobus is a script-based worm. It consists of a few mIRC scripts and batch files. The worm is spread in a self-extracting archive that beside the Ircobus worm drops DoS (Denial of Service) trojans, a modified mIRC client that works with worm's scripts and a few utilities including HideWindow (hides application windows) and PsExec (starts or kills processes on a remote computer)
Based on the settings of your F-Secure security product, it will either move the file to the quarantine where it cannot spread or cause harm, or remove it.
When the self-extracting archive is run by a user, it hiddenly drops a few files to \%winsysdir%\drivers\media\cat32\ folder. Then a startup key is created for the modified mIRC file so that it could be loaded during all Windows sessions.
When the modified mIRC client is started, it loads a few scripts including the Ircobus worm script. The script looks for network shares with the help of external utilities, builds a list of vulnerable computers and then spreads to these computers by copying the dropper file to remote hard disks. The dropper is then activated with the help of PsExec.exe utility and a remote computer becomes infected.
Do disinfect a system it's enough to delete all worm's files as well as a modified mIRC client file and DoS tools.
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