Analysis by: Lord Alfred Remorin
ALIASES:

Backdoor:Win32/Etumbot.gen (Microsoft), a variant of Win32/Agent.PBV (ESET)

 PLATFORM:

Windows 2000, Windows XP, Windows Server 2003

 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 deletes the initially executed copy of itself.

  TECHNICAL DETAILS

Ports: TCP Port 443
File Size: 53,760 bytes
File Type: EXE
Memory Resident: Yes
Initial Samples Received Date: 10 Aug 2012
Payload: Connects to URLs/IPs

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:

  • %User Profile%\Application Data\Microsoft\sidebar.exe

(Note: %User Profile% is the current user's profile folder, which is usually C:\Windows\Profiles\{user name} on Windows 98 and ME, C:\WINNT\Profiles\{user name} on Windows NT, and C:\Documents and Settings\{user name} on Windows 2000, XP, and Server 2003.)

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
sidebar = "%User Profile%\Application Data\Microsoft\sidebar.exe"

Other Details

This backdoor connects to the following possibly malicious URL:

  • {BLOCKED}.{BLOCKED}.13.20:443

It deletes the initially executed copy of itself

  SOLUTION

Minimum Scan Engine: 9.200
FIRST VSAPI PATTERN FILE: 9.312.03
FIRST VSAPI PATTERN DATE: 10 Aug 2012
VSAPI OPR PATTERN File: 9.313.00
VSAPI OPR PATTERN Date: 10 Aug 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

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
    • sidebar = "%User Profile%\Application Data\Microsoft\sidebar.exe"

Step 4

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