Analysis by: Jennifer Gumban
ALIASES:

Worm:Win32/Gamarue (Microsoft), Trojan-Dropper.Win32.Dorifel (Ikarus), Trojan-Dropper.Win32.Dorifel.afkq (Kaspersky)

 PLATFORM:

Windows 2000, Windows Server 2003, Windows XP (32-bit, 64-bit), Windows Vista (32-bit, 64-bit), Windows 7 (32-bit, 64-bit)

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

  • Threat Type: Worm

  • Destructiveness: No

  • Encrypted:

  • In the wild: Yes

  OVERVIEW

This worm arrives on a system as a file dropped by other malware or as a file downloaded unknowingly by users when visiting malicious sites.

It modifies the Internet Explorer Zone Settings.

It deletes itself after execution.

  TECHNICAL DETAILS

File Size: 26,112 bytes
Memory Resident: Yes
Initial Samples Received Date: 04 Jul 2013

Arrival Details

This worm arrives on a system as a file dropped by other malware or as a file downloaded unknowingly by users when visiting malicious sites.

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
{Random GUID} = "%Application Data%\{Random Folder Name}\{Random File Name}.exe"

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\policies\
Explorer\Run
{Random Number} = "%User Profile%\{Random File Name}.exe"

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\Run
SunJavaUpdateSched = "%All Users Profile%\svchost.exe"

Other System Modifications

This worm adds the following registry entries:

HKEY_CURRENT_USER\Identities
Identity Login = "{Random Numbers}"

HKEY_CURRENT_USER\Identities
Identity Ordinal = "2"

HKEY_CURRENT_USER\Identities
Last User ID = "{Random GUID}"

HKEY_CURRENT_USER\Identities
Last Username = "Main Identity"

HKEY_CURRENT_USER\Software\Microsoft\
{Random Key Name}
{Random Name} = "{Random Hex Values}"

Web Browser Home Page and Search Page Modification

This worm modifies the Internet Explorer Zone Settings.

Other Details

This worm connects to the following possibly malicious URL:

  • http://{BLOCKED}ales.pl/buy.php
  • http://{BLOCKED}tudio.pl
  • http://{BLOCKED}t.pl/orders.php
  • http://{BLOCKED}ly.ru/black.php

It drops the following file(s)/component(s):

  • %All Users Profile%\svchost.exe
  • %All Users Profile%\{Random File Name}.exe
  • %Application Data{Random Folder Name}\{Random File Name}.exe
  • %TEMP%\{Random File Name}.exe
  • %TEMP%\{Random File Name}.bat

(Note: %All Users Profile% is the All Users or Common profile folder, which is C:\Documents and Settings\All Users in Windows 2000, XP, and Server 2003, and C:\ProgramData in Windows Vista and 7.)

It deletes itself after execution.

  SOLUTION

Minimum Scan Engine: 9.300
FIRST VSAPI PATTERN FILE: 10.160.03
FIRST VSAPI PATTERN DATE: 03 Jul 2013
VSAPI OPR PATTERN File: 10.161.00
VSAPI OPR PATTERN Date: 04 Jul 2013

Step 1

Before doing any scans, Windows XP, Windows Vista, and Windows 7 users must disable System Restore to allow full scanning of their computers.

Step 2

Scan your computer with your Trend Micro product and note files detected as WORM_GAMARUE.GM

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\Identities
    • Identity Login = "{Random Numbers}"
  • In HKEY_CURRENT_USER\Identities
    • Identity Ordinal = "2"
  • In HKEY_CURRENT_USER\Identities
    • Last User ID = "{Random GUID}"
  • In HKEY_CURRENT_USER\Identities
    • Last Username = "Main Identity"
  • In HKEY_CURRENT_USER\Software\Microsoft\{Random Key Name}
    • {Random Name} = "{Random Hex Values}"
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Run
    • {Random GUID} = "%Application Data%\{Random Folder Name}\{Random File Name}.exe"
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\policies\Explorer\Run
    • {Random Number} = "%User Profile%\{Random File Name}.exe"
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Run
    • SunJavaUpdateSched = "%All Users Profile%\svchost.exe"

Step 5

Search and delete files detected as WORM_GAMARUE.GM

[ 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.
  • %All Users Profile%\svchost.exe
  • %All Users Profile%\{Random File Name}.exe
  • %Application Data{Random Folder Name}\{Random File Name}.exe
  • %TEMP%\{Random File Name}.exe
  • %TEMP%\{Random File Name}.bat

Step 6

Reset Internet security settings

[ Learn More ]

Step 7

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