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Alias:Win32.Opaserv.H [CA], WORM_OPASERV.H [Trend], W32/Opaserv-G [Sophos], W32/Opaserv.worm.k [McAfee]
Type:Worm 
Size:21,504 Bytes 
Origin: 
Date:00-00-0000 
Damage:Spreads over unprotected network resources. 
VDF Version:6.23.00.00 
Danger:Low 
Distribution:Medium 

DistributionIt tries to spread over unprotected network resources.

Technical DetailsWhen activated on Windows 95/98/Me computers, Worm/OpaSoft.F checks for 'GustavVED' in the registry entry:
HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion\Run
If present, the related file is deleted. If not, the worm checks for 'instit' in the entry:
HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion\Run
If not present, the worm registers:
HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion\Run instit C:\WINDOWS\instit.bat

Then, it checks if the file C:\Windows\Instit.bat has been activated. If not, the worm is copied into the file and registers:
HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion\Run GustavVED

After controlling the registry and the place of its activity, the worm ensures that it has only one version in system memory, using a Mutex named GustavoDist.
The worm uses a security vulnerability of Microsoft Windows 95/98/Me. It sends single password characters to the network resource for accessing other Windows 95/98/Me files, without knowing the password.
The affected systems are:
Microsoft Windows 95
Microsoft Windows 98
Microsoft Windows 98 Second Edition
Microsoft Windows Me

It creates C:\Institu, that contains the text
'run=c:\Windows\Brasil.exe,c:\Windows\Brasil.pif, c:\Windows\marco!.scr,c:\windows\scrsvr.exe,c:\windows\instit.bat '.

It looks like the worm is able to update itself, reading files from a website.
It also tries to download a file named Tavinh.scr.
Description inserted by Crony Walker on Tuesday, June 15, 2004

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