Graps

Classification

Malware

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Graps, Worm.Win32.Graps, W32/Graps.worm, W32.HLLW.Graps

Summary

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.

Removal

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

Suspect a file is incorrectly detected (a False Positive)?

A False Positive is when a file is incorrectly detected as harmful, usually because its code or behavior resembles known harmful programs. A False Positive will usually be fixed in a subsequent database update without any action needed on your part. If you wish, you may also:

  • Check for the latest database updates

    First check if your F-Secure security program is using the latest detection database updates, then try scanning the file again.

  • Submit a sample

    After checking, if you still believe the file is incorrectly detected, you can submit a sample of it for re-analysis.

    NOTE If the file was moved to quarantine, you need to collect the file from quarantine before you can submit it.

  • Exclude a file from further scanning

    If you are certain that the file is safe and want to continue using it, you can exclude it from further scanning by the F-Secure security product.

    Note You need administrative rights to change the settings.

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Submit a sample

Submit a file or URL for further analysis.

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