TROJ_INJECT.BZR

October 09, 2012
 Analysis by: Cris Nowell Pantanilla
 PLATFORM:

Windows 2000, Windows XP, Windows Server 2003

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

  • Threat Type: Trojan

  • Destructiveness: No

  • Encrypted:

  • In the wild: Yes

  OVERVIEW

This Trojan deletes itself after execution.

  TECHNICAL DETAILS

File Size:

229,376 bytes

File Type:

EXE

Memory Resident:

Yes

Initial Samples Received Date:

27 Apr 2012

Installation

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

  • %User Temp%\csrssr.exe

(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.)

Autostart Technique

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

HKEY_CURRENT_USER\System\CurrentControlSet\
Services\Run
Windows RPC Host Service = "%User Temp%\csrssr.exe"

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Run
Microsoft Windows Hosting Service = "%User Temp%\csrssr.exe"

HKEY_CURRENT_USER\Software\Microsoft\
Windows NT\CurrentVersion\Winlogon
Microsoft Windows Firewall Service = "%User Temp%\csrssr.exe"

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\Run
Microsoft Windows Hosting Service = "%User Temp%\csrssr.exe"

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows NT\CurrentVersion\Winlogon
Microsoft Windows Firewall Service = "%User Temp%\csrssr.exe"

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\Run
Windows RPC Host Service = "%User Temp%\csrssr.exe"

Other System Modifications

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

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\SharedAccess\Parameters\
FirewallPolicy\StandardProfile\AuthorizedApplications\
List
Microsoft Windows Hosting Service = "%User Temp%\csrssr.exe"

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\policies\
Associations
DefaultFileTypeRisk = "dword:30303030"

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\policies\
Associations
LowRiskFileTypes = ".exe"

Other Details

This Trojan connects to the following possibly malicious URL:

  • r2m.{BLOCKED}o.org

It deletes itself after execution.

  SOLUTION

Minimum Scan Engine:

9.200

FIRST VSAPI PATTERN FILE:

9.236.07

FIRST VSAPI PATTERN DATE:

27 Apr 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

Identify and terminate files detected as TROJ_INJECT.BZR

[ Learn More ]
  1. If the detected file is displayed in either Windows Task Manager or Process Explorer but you cannot delete it, restart your computer in safe mode. To do this, refer to this link for the complete steps.
  2. If the detected file is not displayed in either Windows Task Manager or Process Explorer, continue doing the next steps.

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\System\CurrentControlSet\Services\Run
    • Windows RPC Host Service = "%User Temp%\csrssr.exe"
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Run
    • Microsoft Windows Hosting Service = "%User Temp%\csrssr.exe"
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows NT\CurrentVersion\Winlogon
    • Microsoft Windows Firewall Service = "%User Temp%\csrssr.exe"
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Run
    • Microsoft Windows Hosting Service = "%User Temp%\csrssr.exe"
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Winlogon
    • Microsoft Windows Firewall Service = "%User Temp%\csrssr.exe"
  • In HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Run
    • Windows RPC Host Service = "%User Temp%\csrssr.exe"
  • In HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\SharedAccess\Parameters\FirewallPolicy\StandardProfile\AuthorizedApplications\List
    • Microsoft Windows Hosting Service = "%User Temp%\csrssr.exe"
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\policies\Associations
    • DefaultFileTypeRisk = "dword:30303030"
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\policies\Associations
    • LowRiskFileTypes = ".exe"

Step 4

Scan your computer with your Trend Micro product to delete files detected as TROJ_INJECT.BZR. 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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