Analysis by: Rika Joi Gregorio
ALIASES:

Worm:Win32/Cridex.E(Microsoft), W32.Cridex(Symantec), PWS-Zbot.gen.ad(McAfee), Win32/Cridex.AA worm(Eset)

 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 itself after execution.

  TECHNICAL DETAILS

File Size: 114,688 bytes
File Type: EXE
Memory Resident: Yes
Initial Samples Received Date: 27 Feb 2013

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:

  • %Application Data%\KB{random digits}.exe

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

It creates the following folders:

  • %Application Data%\D184B802

(Note: %Application Data% is the current user's Application Data folder, which is usually C:\Documents and Settings\{user name}\Application Data on Windows 2000, XP, and Server 2003, or C:\Users\{user name}\AppData\Roaming 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 digits}.exe = "%Application Data%\KB{random digits}.exe"

Other System Modifications

This worm adds the following registry keys:

HKEY_CURRENT_USER\Software\Microsoft\
Windows Media Center\{random 1}

HKEY_CURRENT_USER\Software\Microsoft\
Windows Media Center\{random 2}

It adds the following registry entries:

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

Other Details

This worm connects to the following possibly malicious URL:

  • http://{BLOCKED}.{BLOCKED}.234.138:8080/{encrypted information}
  • http://{BLOCKED}.{BLOCKED}.213.178:8080/{encrypted information}
  • http://{BLOCKED}.{BLOCKED}.96.241:8080/{encrypted information}
  • http://{BLOCKED}.{BLOCKED}.217.8:8080/{encrypted information}
  • http://{BLOCKED}.{BLOCKED}.22.90:8080/{encrypted information}
  • http://{BLOCKED}.{BLOCKED}.234.53:8080/{encrypted information}
  • http://{BLOCKED}.{BLOCKED}.186.246:8080/{encrypted information}
  • http://{BLOCKED}.{BLOCKED}.23.100:8080/{encrypted information}
  • http://{BLOCKED}.{BLOCKED}.63.82:8080/{encrypted information}
  • http://{BLOCKED}.{BLOCKED}.74.5:8080/{encrypted information}
  • http://{BLOCKED}.{BLOCKED}.48.6:8080/{encrypted information}
  • http://{BLOCKED}.{BLOCKED}.103.101:8080/{encrypted information}
  • http://{BLOCKED}.{BLOCKED}.53.168:8080/{encrypted information}
  • http://{BLOCKED}.{BLOCKED}.206.90:8080/{encrypted information}
  • http://{BLOCKED}.{BLOCKED}.33.21:8080/{encrypted information}
  • http://{BLOCKED}.{BLOCKED}.228.130:8080/{encrypted information}
  • http://{BLOCKED}.{BLOCKED}.143.90:8080/{encrypted information}
  • http://{BLOCKED}.{BLOCKED}.156.20:8080/{encrypted information}

It deletes itself after execution.

  SOLUTION

Minimum Scan Engine: 9.700
FIRST VSAPI PATTERN FILE: 9.824.06
FIRST VSAPI PATTERN DATE: 29 Mar 2013
VSAPI OPR PATTERN File: 9.825.00
VSAPI OPR PATTERN Date: 29 Mar 2013

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 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 Media Center
    • {random 1}
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows Media Center
    • {random 2}

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\Run
    • KB{random digits}.exe = "%Application Data%\KB{random digits}.exe"
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Internet Settings
    • GlobalUserOffline = "0"

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%\D184B802

Step 6

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