Threat description


Platform: W32


Graps worm was discovered in the beginning of July 2003. This worm spreads in local networks. It scans a network for vulnerable computers and tries to get access the IPC$ and ADMIN$ shares by performing a dictionary attack (using a set of pre-defined weak passwords to get access). If the worm succeeds, it copies itself to remote computer, activates its file and deletes IPC$ and ADMIN$ shares.


To disinfect a system it's enough to delete mwd.exe file and 3 above mentioned batch files from a hard disk.

Technical Details

The worm is a 53kb Windows PE executable file written in Visual Basic and compressed with UPX file compressor. The worm spreads itself with the help of the following files:

psexec.exe - a utility that allows to run processes on remote computers  mswinsck.ocx - standard WinSock library for VB applications  wds.bat  \  wds2.bat  - batch files that spread the worm to remote computers (dropped by the worm)  wds3.bat /  mwd.exe - the worm's executable file  

The batch scripts that the worm drop are used to get access to IPC$ and ADMIN$ share protected by a weak password or no password at all. When such a share is discovered, the scripts copy the worm's main file mwd.exe and also psexec.exe and mswinsck.ocx files to \ADMIN$\System32\ folder (which is a Windows System folder on a remote computer) and start the worm's file remotely with psexec.exe utility. As a result a remote computer becomes infected with the worm. After spreading the worm tries to delete IPC$ and ADMIN$ shares.

On an infected computer the worm creates a startup key for its file in System Registry:

[HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion\Run]  "Windows Management Instumentation" = "%winsysdir%\mwd.exe"  

The worm has a few additional features. It listens to the specific port and can allow remote hackers to log into it and perform the following actions:

- perform DoS (Denial of Service) attack  - get system information  - search for specified files on a hard disk  - redirect traffic (works as a proxy)  - scan for open ports  


Detection for Graps worm is available since the following FSAV updates: Detection Type:PC

Description Details: F-Secure Anti-Virus Research Team; F-Secure Corp.; July 8th, 2003


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