Analysis by: Joie Salvio
ALIASES:

Worm:Win32/Gamarue.F (Microsoft), W32/Gamarue-BK (SOPHOS)

 PLATFORM:

Windows 2000, Windows XP, Windows Server 2003

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

  • Threat Type: Backdoor

  • Destructiveness: No

  • Encrypted:

  • In the wild: Yes

  OVERVIEW

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

It deletes the initially executed copy of itself.

  TECHNICAL DETAILS

File Size: 108,625 bytes
File Type: EXE
Memory Resident: Yes
Initial Samples Received Date: 31 Aug 2013

Arrival Details

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

Installation

This backdoor drops the following copies of itself into the affected system and executes them:

  • %All Users Profile%\Local Settings\Temp\cc{random characters}.{varying extension name}

(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.)

Autostart Technique

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

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\policies\
Explorer\Run
{random number} = "%All Users Profile%\Local Settings\Temp\cc{random characters}.{varying extension name}"

Other Details

This backdoor connects to the following possibly malicious URL:

  • http://{BLOCKED}d.ru/static.php
  • http://{BLOCKED}iuojy.ru/2ldr.php
  • http://{BLOCKED}iuojy.ru/3ldr.php
  • http://{BLOCKED}iuojy.ru/41ldr.php
  • http://{BLOCKED}iuojy.ru/51ldr.php
  • http://{BLOCKED}iuojy.ru/6ldr.php

It deletes the initially executed copy of itself

NOTES:

The {varying extension name} contained in the malware's file name can be any of the following:

  • exe
  • com
  • scr
  • pif
  • cmd
  • bat

  SOLUTION

Minimum Scan Engine: 9.300
FIRST VSAPI PATTERN FILE: 10.254.02
FIRST VSAPI PATTERN DATE: 02 Sep 2013
VSAPI OPR PATTERN File: 10.255.00
VSAPI OPR PATTERN Date: 03 Sep 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

Restart in Safe Mode

[ Learn More ]

Step 3

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_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\policies\Explorer\Run
    • {random number} = "%All Users Profile%\Local Settings\Temp\cc{random characters}.{varying extension name}"

Step 4

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