Win32/Opaserv

Win32/Opaserv primarily targets computers running Microsoft Windows 95, Microsoft Windows 98, or Microsoft Windows ME. The worm modifies files and registry keys in order to run each time Windows starts. 

 

The worm spreads by exploiting the Windows vulnerability described in Microsoft Security Bulletin MS00-072. This vulnerability allows access to password-protected network shares using only the first character of the password. The worm first scans through a UDP port at various IP addresses. If the worm receives a reply, it can connect to drive C through another UDP port if the drive is shared and the computer does not have MS00-072 installed. The worm copies itself to C:\Windows after it connects to the remote computer. It then modifies the win.ini file there so that the worm runs each time Windows starts. 

 

Win32/Opaserv can send infection notifications to attackers or update itself using HTTP. The worm creates temporary .dat files for scripts that it downloads to the infected computer from the Web site. 

 

Under certain conditions, one or more Win32/Opaserv variants may drop a Trojan that can cause the computer to restart. The Trojan can also delete or overwrite critical system files or portions of the hard drive, which can prevent the computer from restarting. The worm may also display a fake warning to the effect that an illegal Microsoft Windows license has been detected.