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Aliases: TrojanSpy:JS/Gauss.plugin!A (Microsoft), Trojan-Spy.Win32.Gauss.script (Kaspersky), W32.Gauss (Norton), PWS-Gauss (NAI), W32/Gauss-A (Sophos), Trojan.Win32.Gauss.script (v) (Sunbelt), Trojan.Spy.Gauss.Plugin.A (Bitdefender), W32/Gauss.A (Fortinet), Trojan-Spy.JS.Gauss (Ikarus)
Malware type: Spyware
Destructive: No
Platform: Windows 2000, Windows XP, Windows Server 2003
In the wild: Yes


This spyware may be dropped by other malware.

It creates folders where it drops its files.

It requires its main component to successfully perform its intended routine. It presents itself as a plugin/add-on/extension for certain applications.

Technical Details

File size: 12,292 bytes
File type: , JS
Memory resident: No
Initial samples received date: 10 Aug 2012

Arrival Details

This spyware may be dropped by the following malware:


It creates the following folders:

  • %Application Data%\Mozilla\Firefox\Profiles\{a288cad4-7b24-43f8-9f4d-8e156305a8bc}

(Note: %Application Data% is the current user's Application Data folder, which is usually C:\Windows\Profiles\{user name}\Application Data on Windows 98 and ME, C:\WINNT\Profiles\{user name}\Application Data on Windows NT, and C:\Documents and Settings\{user name}\Local Settings\Application Data on Windows 2000, XP, and Server 2003.)

Information Theft

This spyware gathers the following data:

  • Browsing history
  • Passwords
  • Cookies

Other Details

This spyware requires its main component to successfully perform its intended routine.

It presents itself as a plugin/add-on/extension for the following applications:

  • Mozilla Firefox


This malicious JavaScript also creates the following log files in the folder it creates:

  • lddp.dat
  • lfm.dat
  • mppd.dat
  • rssf.dat


Minimum scan engine: 9.200
First VSAPI Pattern File: 9.320.02
First VSAPI Pattern Release Date: 13 Aug 2012
VSAPI OPR Pattern Version: 9.321.00
VSAPI OPR Pattern Release Date: 14 Aug 2012

Step 1

For Windows XP and Windows Server 2003 users, before doing any scans, please make sure you disable System Restore to allow full scanning of your computer.

Step 2

Remove malware/grayware files that dropped/downloaded JS_GAUSS.A

Step 3

Search and delete this folder

[ Learn more ]
Please make sure you check the Search Hidden Files and Folders checkbox in the More advanced options option to include all hidden folders in the search result.
  • {a288cad4-7b24-43f8-9f4d-8e156305a8bc}

Step 4

Scan your computer with your Trend Micro product to delete files detected as JS_GAUSS.A. If the detected files have already been cleaned, deleted, or quarantined by your Trend Micro product, no further step is required. You may opt to simply delete the quarantined files. Please check this Knowledge Base page for more information.

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Analysis By: Jasen Sumalapao

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