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TROJ_ZACCESS.RUI

October 09, 2012
 Analysis by: Christopher Daniel So
 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

Infection Channel:

Dropped by other malware, Downloaded from the Internet


This Trojan connects to certain URLs to send and receive commands from a remote malicious user. It terminates processes, some of which are related to system security.

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 does not have any propagation routine.

It does not have any backdoor routine.

It does not have any information-stealing capability.

It deletes itself after execution.

  TECHNICAL DETAILS

File Size:

187,904 bytes

File Type:

EXE

Memory Resident:

Yes

Initial Samples Received Date:

03 Aug 2012

Payload:

Drops files, Connects to URLs/IPs, Terminates processes, Compromises system security

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 injects itself into the following processes running in the affected system's memory:

  • svchost.exe

It creates the following folders:

  • %Application Data%\{b7c1dda7-fb2c-9bfa-9fc6-8da7b93982d2}
  • %Application Data%\{b7c1dda7-fb2c-9bfa-9fc6-8da7b93982d2}\L
  • %Application Data%\{b7c1dda7-fb2c-9bfa-9fc6-8da7b93982d2}\U
  • %Windows%\Installer\{b7c1dda7-fb2c-9bfa-9fc6-8da7b93982d2}
  • %Windows%\Installer\{b7c1dda7-fb2c-9bfa-9fc6-8da7b93982d2}\L
  • %Windows%\Installer\{b7c1dda7-fb2c-9bfa-9fc6-8da7b93982d2}\U

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

Other System Modifications

This Trojan adds the following registry keys:

HKEY_CURRENT_USER\Software\Classes\
CLSID\{42aedc87-2188-41fd-b9a3-0c966feabec1}

It adds the following registry entries as part of its installation routine:

HKEY_CURRENT_USER\Software\Classes\
CLSID\{42aedc87-2188-41fd-b9a3-0c966feabec1}\InprocServer32
(Default) = "%Application Data%\{b7c1dda7-fb2c-9bfa-9fc6-8da7b93982d2}\n."

It modifies the following registry entries:

HKEY_CLASSES_ROOT\CLSID\{42aedc87-2188-41fd-b9a3-0c966feabec1}\
InProcServer32
(Default) = "%Application Data%\{b7c1dda7-fb2c-9bfa-9fc6-8da7b93982d2}\n."

(Note: The default value data of the said registry entry is %SystemRoot%\system32\shdocvw.dll.)

HKEY_CLASSES_ROOT\CLSID\{F3130CDB-AA52-4C3A-AB32-85FFC23AF9C1}\
InprocServer32
(Default) = "\.\globalroot\systemroot\Installer\{b7c1dda7-fb2c-9bfa-9fc6-8da7b93982d2}\n."

(Note: The default value data of the said registry entry is %System%\wbem\wbemess.dll.)

It deletes the following registry keys:

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\BITS

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\SharedAccess

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\wscsvc

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\wuauserv

Propagation

This Trojan does not have any propagation routine.

Backdoor Routine

This Trojan does not have any backdoor routine.

Dropping Routine

This Trojan drops the following files:

  • %Application Data%\{b7c1dda7-fb2c-9bfa-9fc6-8da7b93982d2}\@ - detected by Trend Micro as MAL_XIN12
  • %Windows%\Installer\{b7c1dda7-fb2c-9bfa-9fc6-8da7b93982d2}\@ - detected by Trend Micro as MAL_XIN12
  • %Application Data%\{b7c1dda7-fb2c-9bfa-9fc6-8da7b93982d2}\n - detected by Trend Micro as TROJ_SIREFEF.YP
  • %Windows%\Installer\{b7c1dda7-fb2c-9bfa-9fc6-8da7b93982d2}\n - detected by Trend Micro as TROJ_SIREFEF.YP

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

Information Theft

This Trojan does not have any information-stealing capability.

Other Details

This Trojan deletes itself after execution.

NOTES:

This Trojan accesses the following site to know its location:

  • http://{BLOCKED}s.fling.com/geo/txt/city.php

It may connect to a peer using port 16464 to download other malware or update copies of itself.

It does not have rootkit capabilities.

It does not exploit any vulnerability.

  SOLUTION

Minimum Scan Engine:

9.200

FIRST VSAPI PATTERN FILE:

9.302.05

FIRST VSAPI PATTERN DATE:

03 Aug 2012

VSAPI OPR PATTERN File:

9.303.00

VSAPI OPR PATTERN Date:

04 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

Remove malware files dropped/downloaded by TROJ_ZACCESS.RUI

Step 3

Restart in Safe Mode

[ Learn More ]

Step 4

Delete this registry key

[ 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\Classes\CLSID
    • {42aedc87-2188-41fd-b9a3-0c966feabec1}

Step 5

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_CLASSES_ROOT\CLSID\{42aedc87-2188-41fd-b9a3-0c966feabec1}\InProcServer32
    • From: (Default) = "%Application Data%\{b7c1dda7-fb2c-9bfa-9fc6-8da7b93982d2}\n."
      To: (Default) = "%SystemRoot%\system32\shdocvw.dll"
  • In HKEY_CLASSES_ROOT\CLSID\{F3130CDB-AA52-4C3A-AB32-85FFC23AF9C1}\InprocServer32
    • From: (Default) = "\.\globalroot\systemroot\Installer\{b7c1dda7-fb2c-9bfa-9fc6-8da7b93982d2}\n."
      To: (Default) = "%System%\wbem\wbemess.dll"

Step 6

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%\{b7c1dda7-fb2c-9bfa-9fc6-8da7b93982d2}
  • %Windows%\Installer\{b7c1dda7-fb2c-9bfa-9fc6-8da7b93982d2}

Step 7

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

Step 8

Restore these deleted registry keys/values from backup

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

  • HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\BITS
  • HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\SharedAccess
  • HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\wscsvc
  • HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\wuauserv


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