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BKDR_XTOB.A

August 15, 2013
 Modified by: Rika Joi Gregorio
 ALIASES:

Trojan:Win32/Scar.V (Microsoft), W32.Pilleuz (Norton), Troj/FakeAV-FNY (Sophos), PWS-Zbot.gen.yx (NAI)

 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:

  • 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.

  TECHNICAL DETAILS

File Size:

195072 bytes

File Type:

EXE

Memory Resident:

No

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:

  • %System%\{random file name}.exe - for OS versions Windows XP and lower
  • %Application Data%\Security Data\{random file name}.exe - for OS versions Windows 7 and Vista

(Note: %System% is the Windows system folder, which is usually C:\Windows\System32.. %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.)

It creates the following folders:

  • %Application Data%\Security Data - for OS versions Windows 7 and Vista

(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
{random file name}.exe = "%System%\{random file name}.exe" - for OS versions Windows XP and lower

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Run
{random file name}.exe = "%Application Data%\Security Data\{random file name}.exe" - for OS versions Windows 7 and Vista

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
{random file name}.exe = "%System%\{random file name}.exe" - for OS versions Windows XP and lower

Other Details

This backdoor connects to the following possibly malicious URL:

  • http://{BLOCKED}supdate.{BLOCKED}lo.com/ping.php
  • http://{BLOCKED}supdate.{BLOCKED}lo.com/sedo.php

NOTES:

The dropped copy's file path and name may depend on the affected machine's OS version.

The file name and registry value name {random file name} can be any of the following:

  • Windows
  • Components
  • Audio
  • Storage
  • Profile
  • Data
  • Resources
  • Deamonu
  • Loader
  • Guard
  • WinProtect
  • WinShield
  • WinGuard

  SOLUTION

Minimum Scan Engine:

9.300

VSAPI OPR PATTERN File:

9.864.04

VSAPI OPR PATTERN Date:

28 May 2012

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

Search and delete these folders

[ Learn More ]
Please make sure you check the Search Hidden Files and Folders checkbox in the More advanced options option to include all hidden folders in the search result.
  • %Application Data%\Security Data

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_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Run
    • {random file name}.exe = "%System%\{random file name}.exe"
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Run
    • {random file name}.exe = "%Application Data%\Security Data\{random file name}.exe"
  • In HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\SharedAccess\Parameters\FirewallPolicy\StandardProfile\AuthorizedApplications\List
    • {random file name}.exe = "%System%\{random file name}.exe"

Step 5

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