Threat Descriptions

Trojan-Proxy:W32/Grum.A

Classification

Category :

Malware

Type :

Trojan-Proxy

Platform :

W32

Aliases :

Trojan-Proxy:W32/Grum.A

Summary

This trojan allows unauthorized parties to use the infected computer as a proxy server to anonymously access the Internet.

Removal

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.

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 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.

Technical Details

Trojan-Proxy:W32/Grum.A may arrive in the system in a spam email message containing an image that links to the real malware.

Here is the image associated with the message:

This malware is hosted at the following links:

  • http://tvz-archive.com/I[REMOVED}.exe
  • http://abnoba.net/I[REMOVED]0.exe

Click here for details about spam on our weblog.

Installation

If the user executes the file they are directed to by the spam message, it creates a copy of itself on the user's computer at the following path and filename:

  • %temp%\winlogon.exe

Grum.A uses the following batch file created on the same directory where the malware was to delete the executed copy of itself:

  • sys.bat

To enable automatic execution upon system boot, it adds the following auto start registry:

  • HKCU\\Software\Microsoft\Windows\CurrentVersion\Run Firewall auto setup = %temp%\winlogon.exe

Note: %temp% is the temporary windows folder:

Activity

Once installed, Grum.A serves as a proxy server that communicates to the following address:

  • 72.232.49.214

Commands from the server may include downloading of files and spamming mails.

Stealth

Grum.A is a kernel malware that hooks several ntdll APIs to hide its file and process.