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WORM_CRIDEX.OD

February 14, 2014
 Analysis by: Alvin John Nieto
 ALIASES:

Worm:Win32/Cridex.E (Microsoft), Trojan.Win32.Cridex.tau (v) (Sunbelt), Trojan-Spy.Win32.Zbot.quwm (Kaspersky)

 PLATFORM:

Windows 2000, Windows Server 2003, Windows XP (32-bit, 64-bit), Windows Vista (32-bit, 64-bit), Windows 7 (32-bit, 64-bit)

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

  • 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.

It deletes the initially executed copy of itself.

  TECHNICAL DETAILS

File Size:

117,248 bytes

File Type:

EXE

Memory Resident:

Yes

Initial Samples Received Date:

07 Feb 2014

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 and executes them:

  • %User Profile%\Application Data\KB{8 random numbers}.exe

(Note: %User Profile% is the current user's profile folder, which is usually C:\Documents and Settings\{user name} on Windows 2000, XP, and Server 2003, or C:\Users\{user name} on Windows Vista and 7.)

It creates the following folders:

  • %User Profile%\Application Data\{random string 1}

(Note: %User Profile% is the current user's profile folder, which is usually C:\Documents and Settings\{user name} on Windows 2000, XP, and Server 2003, or C:\Users\{user name} on Windows Vista and 7.)

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
KB{random number}.exe = "%User Profile%\Application Data\KB{random number}.exe"

Other System Modifications

This worm adds the following registry keys:

HKEY_CURRENT_USER\Software\Microsoft\
Windows NT\{random character}{random string 1}

HKEY_CURRENT_USER\Software\Microsoft\
Windows NT\{random string 2}

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

Other Details

This worm connects to the following possibly malicious URL:

  • http://{BLOCKED}srvr8.ru/{random characters}
  • http://{BLOCKED}load.ru/{random characters}
  • http://{BLOCKED}sdnl.ru/{random characters}
  • http://{BLOCKED}ownloads17.ru/{random characters}

It deletes the initially executed copy of itself

  SOLUTION

Minimum Scan Engine:

9.700

FIRST VSAPI PATTERN FILE:

10.594.02

FIRST VSAPI PATTERN DATE:

09 Feb 2014

VSAPI OPR PATTERN File:

10.595.00

VSAPI OPR PATTERN Date:

09 Feb 2014

Step 1

Before doing any scans, Windows XP, Windows Vista, and Windows 7 users must disable System Restore to allow full scanning of their computers.

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
    • KB{8 random numbers}.exe = "%User Profile%\Application Data\KB{8 random numbers}.exe"
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Internet Settings
    • GlobalUSerOffiline = "0"

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\Microsoft\Windows NT
    • {random character}{random string 1}
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows NT
    • {random string 2}

Step 5

Search and delete this folder

[ 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. %User Profile%\Application Data\{random string 1}

Step 6

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

NOTES:
The created hidden folder %User Profile%\Application Data\{random string 1}, along with the created registry keys ;HKEY_CURRENT_USER\Software\Microsoft\Windows NT\{random character}{random string 1} and HKEY_CURRENT_USER\Software\Microsoft\Windows NT\{random string 2}, cannot be identified by the users since there are no reference values in the created folder or keys. The only way these folders/keys can be identified is by comparing the present folders/keys with a backup if the users have one. Note that these folders/keys need not to be deleted since it won't cause the user system any harm.


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