Analysis by: Rika Joi Gregorio

ALIASES:

Backdoor:Win32/Etumbot.gen(Microsoft), Backdoor.Win32.Farfli(Ikarus)

 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

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 does not have any propagation routine.

It runs certain commands that it receives remotely from a malicious user. Doing this puts the affected computer and information found on the computer at greater risk.

It connects to certain websites to send and receive information.

  TECHNICAL DETAILS

File Size: 81,408 bytes
File Type: EXE
Memory Resident: Yes
Initial Samples Received Date: 15 May 2013
Payload: Connects to URLs/IPs, Drops files, 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 files:

  • %User Temp%\~DF4E74.doc

(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.)

It drops and executes the following files:

  • %Application Data%\Microsoft\Windows\WindowsUpdate.exe - detected as BKDR_ETUMBOT.AKV

(Note: %Application Data% is the current user's Application Data folder, which is usually C:\Documents and Settings\{user name}\Application Data on Windows 2000, XP, and Server 2003, or C:\Users\{user name}\AppData\Roaming on Windows Vista and 7.)

Autostart Technique

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

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Run
WindowsUpdate = "%Application Data%\Microsoft\Windows\WindowsUpdate.exe"

Propagation

This backdoor does not have any propagation routine.

Backdoor Routine

This backdoor executes the following command(s) from a remote malicious user:

  • Perform Remote Shell
  • Download Files
  • Upload Files
  • Execute Files
  • Sleep

Information Theft

This backdoor gathers the following data:

  • User Name
  • Computer Name
  • IP Address
  • OS Version
  • Proxy Server

Other Details

This backdoor connects to the following website to send and receive information:

  • http://{BLOCKED}.{BLOCKED}.46.102:443/XEL{random digits}={random digits}.cgi?{Encrypted Information}

It opens the following files:

  • %User Temp%\~DF4E74.doc

(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.)

NOTES:
Where {Encrypted Information} contains encrypted User Name, Host Name, IP Address, OS Version, and Proxy Server.

  SOLUTION

Minimum Scan Engine: 9.300
FIRST VSAPI PATTERN FILE: 9.934.05
FIRST VSAPI PATTERN DATE: 22 May 2013
VSAPI OPR PATTERN File: 9.935.00
VSAPI OPR PATTERN Date: 22 May 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_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Run
    • WindowsUpdate = "%Application Data%\Microsoft\Windows\WindowsUpdate.exe"

Step 4

Search and delete this file

[ 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%\~DF4E74.doc

Step 5

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


Did this description help? Tell us how we did.