WORM_CRIDEX.A

October 09, 2012
 Analysis by: Michael Cabel
 PLATFORM:

Windows 2000, Windows XP, Windows Server 2003

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

  • Threat Type: Worm

  • Destructiveness: No

  • Encrypted:

  • In the wild: Yes

  OVERVIEW

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

However, as of this writing, the said sites are inaccessible. It deletes the initially executed copy of itself.

  TECHNICAL DETAILS

File Size:

51,200 bytes

File Type:

EXE

Memory Resident:

Yes

Initial Samples Received Date:

09 Sep 2011

Arrival Details

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

  • %Application Data%\BC75E553\BC75E553.EXE

(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.)

It creates the following folders:

  • %Application Data%\BC75E553
  • %Application Data%\10F809D3

(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.)

It injects threads into the following normal process(es):

  • Explorer.exe

Autostart Technique

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

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Run
BC75E553 = "%Application Data%\BC75E553\BC75E553.EXE"

Other System Modifications

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

HKEY_CURRENT_USER\Software\Microsoft\
Security Center

Other Details

This worm connects to the following possibly malicious URL:

  • http://{BLOCKED}hjgoidw.ru

However, as of this writing, the said sites are inaccessible.

It deletes the initially executed copy of itself

  SOLUTION

Minimum Scan Engine:

9.200

FIRST VSAPI PATTERN FILE:

8.418.02

FIRST VSAPI PATTERN DATE:

09 Sep 2011

VSAPI OPR PATTERN File:

8.419.00

VSAPI OPR PATTERN Date:

09 Sep 2011

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 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
    • BC75E553 = "%Application Data%\BC75E553\BC75E553.EXE"

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. 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_CURRENT_USER\Software\Microsoft
    • Security Center

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.
  • %Application Data%\BC75E553
  • %Application Data%\10F809D3

Step 6

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