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TROJ_BAMITAL.QUE

October 08, 2012
 Analysis by: Christopher Daniel So
 ALIASES:

W32/Bamital.j (McAfee), Trojan-Ransom.Win32.PornoBlocker.dgz (Kaspersky), W32/PornoBlocker.DGZ!tr (Fortinet), Win32/Bamital.EZ trojan (Nod32), TR/Ransom.PornoBlocker.dgz (AntiVir), Hoax.PornoBlocker.dgz (Vba32)

 PLATFORM:

Windows 2000, Windows XP, Windows Server 2003

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

  • Threat Type: Trojan

  • Destructiveness: No

  • Encrypted: Yes

  • In the wild: Yes

  OVERVIEW

This Trojan arrives on a system as a file dropped by other malware or as a file downloaded unknowingly by users when visiting malicious sites.

It modifies system files, disabling system programs from properly running.

  TECHNICAL DETAILS

File Size:

57,856 bytes

File Type:

EXE

File Compression:

UPX

Memory Resident:

No

Initial Samples Received Date:

21 Jan 2011

Arrival Details

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

  • %System Root%\Documents and Settings\All Users\Documents\19792079

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

It drops the following files:

  • %Windows%\Temp\explorer.dat - original copy of %Windows%\explorer.dat
  • %Windows%\Temp\winlogon.dat - original copy of %System%\winlogon.exe (if not running Windows Vista or Windows 7)
  • %Windows%\Temp\wininit.dat - original copy of %System%\wininit.exe (if running Windows Vista or Windows 7)

(Note: %Windows% is the Windows folder, which is usually C:\Windows or C:\WINNT.. %System% is the Windows system folder, which is usually C:\Windows\System on Windows 98 and ME, C:\WINNT\System32 on Windows NT and 2000, or C:\Windows\System32 on Windows XP and Server 2003.)

Other System Modifications

This Trojan modifies the following registry entries:

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\sr\Parameters
FirstRun = 1

(Note: The default value data of the said registry entry is 0.)

File Infection

This Trojan patches the following system files:

  • %Windows%\explorer.exe - detected as PTCH_BAMITAL.SMX
  • %System%\winlogon.exe - detected as PTCH_BAMITAL.SMX (if not running Windows Vista/Windows 7)
  • %System%\wininit.exe - detected as PTCH_BAMITAL.SMX (if running Windows Vista/Windows 7)

(Note: %Windows% is the Windows folder, which is usually C:\Windows or C:\WINNT.. %System% is the Windows system folder, which is usually C:\Windows\System on Windows 98 and ME, C:\WINNT\System32 on Windows NT and 2000, or C:\Windows\System32 on Windows XP and Server 2003.)

Dropping Routine

This Trojan drops the following files:

  • %System%\dll - detected as BKDR_BAMITAL.SMZ
  • %System%\nt.dll - detected as TROJ_BAMITAL.SMY

(Note: %System% is the Windows system folder, which is usually C:\Windows\System on Windows 98 and ME, C:\WINNT\System32 on Windows NT and 2000, or C:\Windows\System32 on Windows XP and Server 2003.)

  SOLUTION

Minimum Scan Engine:

8.900

VSAPI PATTERN File:

7.780.15

VSAPI PATTERN Date:

21 Jan 2011

VSAPI PATTERN Date:

1/21/2011 12:00:00 AM

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

Remove malware files dropped/downloaded by TROJ_BAMITAL.QUE

    BKDR_BAMITAL.SMZ
    PTCH_BAMITAL.SMX
    TROJ_BAMITAL.SMY

Step 3

Restore this modified 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\SYSTEM\CurrentControlSet\Services\sr\Parameters
    • From: FirstRun=1
      To: FirstRun=0

Step 4

Restore deleted/modified files and/or registry entries from backup

*Note: Only Microsoft-related files/keys/values will be restored. If this malware/grayware also deleted registry keys/values related to programs that are not from Microsoft, please reinstall those programs on your computer.

    • %Windows%\explorer.dat
    • %System%\winlogon.exe
    • %System%\wininit.exe

Step 5

Scan your computer with your Trend Micro product to delete files detected as TROJ_BAMITAL.QUE. 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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