BKDR_ANDROM.CL

 Analysis by: Rika Joi Gregorio

 ALIASES:

Worm:Win32/Gamarue.I(Microsoft), W32/Yakes.B!tr(Fortinet), Trojan-Spy.Agent(Ikarus), Win32/TrojanDownloader.Wauchos.A trojan(Eset)

 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:

  • Threat Type: Backdoor

  • Destructiveness: No

  • Encrypted: Yes

  • In the wild: Yes

  OVERVIEW

Infection Channel:

Downloaded from the Internet, Dropped by other malware, Spammed via email

This backdoor arrives as an attachment to email messages spammed by other malware/grayware or malicious users.

It executes commands from a remote malicious user, effectively compromising the affected system. It connects to a website to send and receive information.

It does not have any information-stealing capability.

  TECHNICAL DETAILS

File Size:

48,640 bytes

File Type:

EXE

Memory Resident:

Yes

Initial Samples Received Date:

27 Feb 2013

Payload:

Compromises system security, Connects to URLs/IPs, Downloads files

Arrival Details

This backdoor arrives as an attachment to email messages spammed by other malware/grayware or malicious users.

Installation

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

  • %ProgramData%\svchost.exe (Windows Vista and 7 only)
  • {All User's Profile}\svchost.exe
  • {All Users' Profile}\Local Settings\Temp\ms{random characters}.{extension name}

(Note: %ProgramData% is a version of the Program Files folder where any user on a multi-user computer can make changes to programs. This is usually C:\ProgramData in Windows Vista and 7, or C:\Program Files on Windows 2000, XP (32-bit), and Server 2003, or C:\Program Files (x86) on Windows XP (64-bit).)

It adds the following processes:

  • \system32\wuauclt.exe
  • \syswow64\svchost.exe

It injects codes into the following process(es):

  • \system32\wuauclt.exe
  • \syswow64\svchost.exe

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\Run
SunJavaUpdateSched = "{All User's Profile}\svchost.exe"

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\policies\
Explorer\Run
{random digit} = "{All Users' Profile}\Local Settings\Temp\ms{random characters}.{extension name}"

Other System Modifications

This backdoor creates the following registry entry(ies) to bypass Windows Firewall:

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\SharedAccess\Parameters\
FirewallPolicy\StandardProfile\AuthorizedApplications\
List
{malware path}\{malware name}.exe = "{malware path}\{malware name}.exe:*:Enabled:{malware name}"

Backdoor Routine

This backdoor executes the following commands from a remote malicious user:

  • Download a file from C&C server and save it as %User Temp%\{random number}.exe
  • Download a file from C&C server and save it in the folder %System Root%\Documents and Settings\All Users\ms{random number}.dat and loads it
  • Start a process
  • Uninstall itself
  • Remote command prompt

(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, or C:\Users\{user name}\AppData\Local\Temp on Windows Vista and 7.. %System Root% is the root folder, which is usually C:\. It is also where the operating system is located.)

It connects to the following websites to send and receive information:

  • http://{BLOCKED}oss.ru/image.php
  • http://{BLOCKED}ipn.ru/image.php

Information Theft

This backdoor does not have any information-stealing capability.

Other Details

This backdoor connects to the following URL(s) to check for an Internet connection:

  • www.update.microsoft.com

NOTES:

The {extension name} of the dropped copy is any of the following:

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

It checks if it is being run in a VMWare environment. If it is being run in a VMWare environment, it performs another routine where it will open Port 8000 and listen for a backdoor command for performing remote shell execution.

It does not have any information-stealing capability.

  SOLUTION

Minimum Scan Engine:

9.300

FIRST VSAPI PATTERN FILE:

9.756.01

FIRST VSAPI PATTERN DATE:

27 Feb 2013

VSAPI OPR PATTERN File:

9.757.00

VSAPI OPR PATTERN Date:

28 Feb 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\Run
    • SunJavaUpdateSched = "{All User's Profile}\svchost.exe"
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\policies\Explorer\Run
    • {random digit} = "{All Users' Profile}\Local Settings\Temp\ms{random characters}.{extension name}"
  • In HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\SharedAccess\Parameters\FirewallPolicy\StandardProfile\AuthorizedApplications\List
    • {malware path}\{malware name}.exe = "{malware path}\{malware name}.exe:*:Enabled:{malware name}"

Step 4

Search and delete these files

[ Learn More ]
There may be some files that are hidden. Please make sure you check the Search Hidden Files and Folders checkbox in the "More advanced options" option to include all hidden files and folders in the search result.
  • %User Temp%\{random number}.exe
  • %System Root%\Documents and Settings\All Users\ms{random number}.dat

Step 5

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