BKDR_ANDROM.B

October 09, 2012
 Analysis by: Jed Valderama
 ALIASES:

Worm:Win32/Gamarue.I (Microsoft), Generic BackDoor.abd (McAfee), a variant of Win32/Kryptik.ALNP trojan (Nod32), W32/Androm.DW!tr (Fortinet), Trojan.Win32.Generic!BT (Sunbelt)

 PLATFORM:

Windows 2000, Windows XP, Windows Server 2003

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

  • Threat Type: Backdoor

  • Destructiveness: No

  • Encrypted: No

  • In the wild: Yes

  OVERVIEW

Infection Channel:

Dropped by other malware, Downloaded from the Internet

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 executes commands from a remote malicious user, effectively compromising the affected system.

It deletes the initially executed copy of itself.

  TECHNICAL DETAILS

Ports:

TCP Port 80 (HTTP)

File Size:

51,200 bytes

File Type:

EXE

Memory Resident:

Yes

Initial Samples Received Date:

08 Sep 2012

Payload:

Connects to URLs/IPs, Compromises system security

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:

  • {All User's Profile}\Local Settings\Temp\ms{random characters}.{extension name}
  • {All User's Profile}\svchost.exe

It adds the following mutexes to ensure that only one of its copies runs at any one time:

  • {Decimal form of the Volume Serial Number of %System Root%}

(Note: %System Root% is the root folder, which is usually C:\. It is also where the operating system is located.)

It injects codes into the following process(es):

  • wuauclt.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 number} = "{All User's Profile}\Local Settings\Temp\ms{random characters}.{extension 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 {All User's Profile}\ms{random number}.dat and loads it
  • Start a process
  • Uninstall itself

(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.)

It connects to the following URL(s) to send and receive commands from a remote malicious user:

  • http://{BLOCKED}e.com/image.php - blocked
  • http://{BLOCKED}ep.ru/image.php - blocked
  • http://{BLOCKED}oes.com/image.php - blocked
  • http://{BLOCKED}m.ru/image.php - blocked
  • http://{BLOCKED}s.com/image.php - blocked
  • http://{BLOCKED}ge.com/image.php - blocked

Other Details

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

  • http://www.update.microsoft.com

It deletes the initially executed copy of itself

NOTES:
Where {extension name} is any of the following:

  • BAT
  • CMD
  • COM
  • EXE
  • PIF
  • SCR

  SOLUTION

Minimum Scan Engine:

9.200

FIRST VSAPI PATTERN FILE:

9.378.06

FIRST VSAPI PATTERN DATE:

08 Sep 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

Scan your computer with your Trend Micro product and note files detected as BKDR_ANDROM.B

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_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 number} = "{All User's Profile}\Local Settings\Temp\ms{random characters}.{extension name}"

Step 5

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