BKDR_CORUM.A

 Analysis by: Sabrina Lei Sioting

 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

This backdoor may arrive bundled with malware packages as a malware component.

It exports functions used by other malware. It deletes the initially executed copy of itself.

  TECHNICAL DETAILS

File Size:

319,488 bytes

File Type:

DLL

Memory Resident:

Yes

Initial Samples Received Date:

04 Apr 2012

Arrival Details

This backdoor may arrive bundled with malware packages as a malware component.

Installation

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

  • %System Root%\Documents and Settings\All Users\Application Data\Microsoft\OpenGL\~{random}.dll
  • %System Root%\Documents and Settings\All Users\Application Data\Microsoft\OpenGL\~3BF.tmp
  • %System Root%\Documents and Settings\All Users\Application Data\Microsoft\OpenGL\~3BF.tmp32
  • %System Root%\Documents and Settings\All Users\Application Data\Microsoft\OpenGL\~3BF.tmp64
  • %System%\MurocApc.dll
  • %System%\Setup\MurocApc.dll
  • {malware path}\~022356.tme

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

It creates the following folders:

  • %System Root%\Documents and Settings\All Users\Application Data\Microsoft\OpenGL
  • %Program Files%\Microsoft\OpenGL
  • %Program Files%\Microsoft\Search Enhancement Pack\OpenGL

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

Autostart Technique

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

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows NT\CurrentVersion\Winlogon\
Notify\ZmEvMon
DLLName = "%Program Files%\Microsoft\OpenGL\MurocApc.dll"

Other System Modifications

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

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Internet Settings
GlobalUserOffline = "0"

HKEY_CURRENT_USER\Software\Sysinternals\
Junction
EulaAccepted = "1"

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\SharedAccess\Parameters\
FirewallPolicy\DomainProfile\AuthorizedApplications\
List
%System%\rundll32.exe = "%System%\rundll32.exe:*:Enabled:Run a DLL as an App"

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

HKEY_CLASSES_ROOT\Briefcase.Server

HKEY_LOCAL_MACHINE\SOFTWARE\Classes\
Briefcase.Server

HKEY_CURRENT_USER\Software\Sysinternals\
Junction

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows NT\CurrentVersion\Winlogon\
Notify\ZmEvMon

Other Details

This backdoor exports functions used by other malware.

It connects to the following possibly malicious URL:

  • http://pere{BLOCKED}bs.com/hj_logo.jpg
  • http://www.{BLOCKED}w.cn/Images/hj_logo.jpg

It deletes the initially executed copy of itself

NOTES:

It copies all folders and files found in the following directories: Operating System major version is 5 (XP, 2000, 2003):
From: %System%\Setup
To: %Program Files%\Microsoft\OpenGL

From: %System%
To: %Program Files%\Microsoft\Search Enhancement Pack\OpenGL

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

  SOLUTION

Minimum Scan Engine:

9.200

FIRST VSAPI PATTERN FILE:

8.884.07

FIRST VSAPI PATTERN DATE:

04 Apr 2012

VSAPI OPR PATTERN File:

8.885.00

VSAPI OPR PATTERN Date:

05 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

Restart in Safe Mode

[ Learn More ]

Step 3

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. Before you could do this, you must restart in Safe Mode. For instructions on how to do this, you may refer to this page If the preceding step requires you to restart in safe mode, you may proceed to edit the system registry.

  • In HKEY_CLASSES_ROOT
    • Briefcase.Server
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Classes
    • Briefcase.Server
  • In HKEY_CURRENT_USER\Software\Sysinternals
    • Junction
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Winlogon\Notify
    • ZmEvMon

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\Internet Settings
    • GlobalUserOffline = "0"
  • In HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\SharedAccess\Parameters\FirewallPolicy\DomainProfile\AuthorizedApplications\List
    • %System%\rundll32.exe = "%System%\rundll32.exe:*:Enabled:Run a DLL as an App"

Step 5

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.
  • %System Root%\Documents and Settings\All Users\Application Data\Microsoft\OpenGL
  • %Program Files%\Microsoft\OpenGL
  • %Program Files%\Microsoft\Search Enhancement Pack\OpenGL

Step 6

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