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WORM_GAMMIM.AB

October 08, 2012
 Analysis by: Kathleen Notario
 PLATFORM:

Windows 2000, XP, Server 2003

 OVERALL RISK RATING:
 DAMAGE POTENTIAL:
 DISTRIBUTION POTENTIAL:
 REPORTED INFECTION:

  • Threat Type: Worm

  • Destructiveness: No

  • Encrypted: No

  • In the wild: Yes

  OVERVIEW

This worm may be downloaded by other malware/grayware/spyware from remote sites. It may be dropped by other malware. It may be unknowingly downloaded by a user while visiting malicious websites.

It drops copies of itself in all removable drives. It drops an AUTORUN.INF file to automatically execute the copies it drops when a user accesses the drives of an affected system.

It executes the downloaded files. As a result, malicious routines of the downloaded files are exhibited on the affected system.

It deletes itself after execution.

  TECHNICAL DETAILS

File Size:

129,536 bytes

File Type:

EXE

File Compression:

Aspack

Memory Resident:

Yes

Initial Samples Received Date:

27 Oct 2010

Payload:

Downloads files, Drops files

Arrival Details

This worm may be downloaded by other malware/grayware/spyware from remote sites.

It may be dropped by other malware.

It may be unknowingly downloaded by a user while visiting malicious websites.

Installation

This worm drops the following copies of itself into the affected system:

  • %User Temp%\doscp.exe

(Note: %User Temp% is the current user's Temp folder, which is usually C:\Documents and Settings\{user name}\Local Settings\Temp on Windows 2000, XP, and Server 2003.)

Autostart Technique

This worm adds the following registry entries to enable its automatic execution at every system startup:

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Run
doscp = %User Temp%\doscp.exe

Other System Modifications

This worm modifies the following registry entries:

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Explorer\
Advanced
Hidden = 2

(Note: The default value data of the said registry entry is 1.)

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Explorer\
Advanced
ShowSuperHidden = 0

(Note: The default value data of the said registry entry is 1.)

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\Explorer\
Advanced\Folder\Hidden\
SHOWALL
CheckedValue = 0

(Note: The default value data of the said registry entry is 1.)

Propagation

This worm drops copies of itself in all removable drives.

It drops an AUTORUN.INF file to automatically execute the copies it drops when a user accesses the drives of an affected system.

The said .INF file contains the following strings:

[AutoRun]
open={random filename}.exe
shell\open\Command={random filename}.exe

Dropping Routine

This worm drops the following files:

  • %User Temp%\doscp{random number}.dll - detected as TSPY_GAMETHI.AB

(Note: %User Temp% is the current user's Temp folder, which is usually C:\Documents and Settings\{user name}\Local Settings\Temp on Windows 2000, XP, and Server 2003.)

Download Routine

This worm connects to the following website(s) to download and execute a malicious file:

  • http://www.{BLOCKED}wf.com/1rb/ar.rar - detected as WORM_TATERF.FQ

It then executes the downloaded files. As a result, malicious routines of the downloaded files are exhibited on the affected system.

Other Details

This worm deletes itself after execution.

  SOLUTION

Minimum Scan Engine:

8.900

VSAPI OPR PATTERN File:

7.572.07

VSAPI OPR PATTERN Date:

27 Oct 2010

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 files dropped/downloaded by WORM_GAMMIM.AB

    TSPY_GAMETHI.AB
    WORM_TATERF.FQ

Step 3

Restart in Safe Mode

[ Learn More ]

Step 4

Delete this registry value

[ Learn More ]

Important: Editing the Windows Registry incorrectly can lead to irreversible system malfunction. Please do this step only if you know how or you can ask assistance from your system administrator. Else, check this Microsoft article first before modifying your computer's registry.

 
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Run
    • doscp = %User Temp%\doscp.exe

Step 5

Restore this modified registry value

[ Learn More ]

Important: Editing the Windows Registry incorrectly can lead to irreversible system malfunction. Please do this step only if you know how or you can ask assistance from your system administrator. Else, check this Microsoft article first before modifying your computer's registry.

  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Explorer\Advanced
    • From: Hidden = 2
      To: 1
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Explorer\Advanced
    • From: ShowSuperHidden = 0
      To: 1
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Explorer\Advanced\Folder\Hidden\SHOWALL
    • From: CheckedValue = 0
      To: 1

Step 6

Search and delete AUTORUN.INF files created by WORM_GAMMIM.AB that contain these strings

[ Learn More ]
[AutoRun]
open={random filename}.exe
shell\open\Command={random filename}.exe

Step 7

Restart in normal mode and scan your computer with your Trend Micro product for files detected as WORM_GAMMIM.AB. 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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