Analysis by: Mark Joseph Manahan
ALIASES:

Worm:Win32/Cridex.E (Microsoft), Win32/Cridex.AA worm (Eset), W32.Cridex (

 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:

  • Threat Type: Backdoor

  • Destructiveness: No

  • Encrypted:

  • In the wild: Yes

  OVERVIEW

This backdoor arrives as an attachment to email messages spammed by other malware/grayware or malicious users.

It executes then deletes itself afterward.

  TECHNICAL DETAILS

File Size: 102,400 bytes
File Type: EXE
Memory Resident: Yes
Initial Samples Received Date: 08 Mar 2013

Arrival Details

This backdoor arrives as an attachment to email messages spammed by other malware/grayware or malicious users.

Installation

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

  • %User Profile%\Application Data\KB{random number}.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 folder}

(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 executes then deletes itself afterward.

Autostart Technique

This backdoor 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 Details

This backdoor connects to the following possibly malicious URL:

  • http://{BLOCKED}9.{BLOCKED}8.106.162:8080
  • http://{BLOCKED}1.{BLOCKED}9.153.206:8080
  • http://{BLOCKED}9.{BLOCKED}6.96.9:8080
  • http://{BLOCKED}1.{BLOCKED}6.35.117:8080
  • http://{BLOCKED}4.{BLOCKED}1.67.199:8080
  • http://{BLOCKED}4.{BLOCKED}3.234.138:8080
  • http://{BLOCKED}8.{BLOCKED}9.3.253:8080
  • http://{BLOCKED}8.{BLOCKED}8.96.241:8080
  • http://{BLOCKED}4.{BLOCKED}9.217.8:8080
  • http://{BLOCKED}4.{BLOCKED}7.99.120:8080
  • http://{BLOCKED}5.{BLOCKED}1.22.97:8080
  • http://{BLOCKED}2.{BLOCKED}9.5.195:8080
  • http://{BLOCKED}3.{BLOCKED}1.234.53:8080
  • http://{BLOCKED}9.{BLOCKED}7.186.246:8080
  • http://{BLOCKED}2.{BLOCKED}8.63.82:8080
  • http://{BLOCKED}3.{BLOCKED}4.74.5:8080
  • http://{BLOCKED}3.{BLOCKED}1.164.83:8080
  • http://{BLOCKED}1.{BLOCKED}.103.101:8080
  • http://{BLOCKED}4.{BLOCKED}5.53.168:8080
  • http://{BLOCKED}2.{BLOCKED}1.206.90:8080
  • http://{BLOCKED}8.{BLOCKED}7.153.131:8080
  • http://{BLOCKED}2.{BLOCKED}0.228.130:8080
  • http://{BLOCKED}5.{BLOCKED}4.143.90:8080
  • http://{BLOCKED}8.{BLOCKED}9.156.20:8080
  • http://{BLOCKED}1.{BLOCKED}9.155.222:8080

  SOLUTION

Minimum Scan Engine: 9.300
FIRST VSAPI PATTERN FILE: 9.774.03
FIRST VSAPI PATTERN DATE: 08 Mar 2013
VSAPI OPR PATTERN File: 9.775.00
VSAPI OPR PATTERN Date: 09 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 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 number}.exe = "%User Profile%\Application Data\KB{random number}.exe"

Step 4

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 folder}

Step 5

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