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TROJ_MEDFOS.AIJ

March 18, 2013
 Analysis by: Christopher Daniel So
 ALIASES:

Trojan:Win32/Medfos.B (Microsoft), Medfos.ai (McAfee)

 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: Trojan

  • Destructiveness: No

  • Encrypted:

  • In the wild: Yes

  OVERVIEW

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

  TECHNICAL DETAILS

File Size:

472,064 bytes

File Type:

DLL

Initial Samples Received Date:

22 Jan 2013

Arrival Details

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

Other System Modifications

This Trojan adds the following registry keys:

HKEY_LOCAL_MACHINE\SOFTWARE\Google\
Chrome\Extensions\cdjbnddbclciabnckgeahmneohjlahdm

It adds the following registry entries:

HKEY_LOCAL_MACHINE\SOFTWARE\Google\
Chrome\Extensions\cdjbnddbclciabnckgeahmneohjlahdm
path = "%AppDataLocal%\chromeupdate.crx"

HKEY_LOCAL_MACHINE\SOFTWARE\Google\
Chrome\Extensions\cdjbnddbclciabnckgeahmneohjlahdm
version = "1.0"

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion
{malware file name} = "ODUuMTcuMTMyLjU0OwAA"

Dropping Routine

This Trojan drops the following files:

  • %AppDataLocal%\chromeupdate.crx

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

  SOLUTION

Minimum Scan Engine:

9.300

FIRST VSAPI PATTERN FILE:

9.674.04

FIRST VSAPI PATTERN DATE:

23 Jan 2013

VSAPI OPR PATTERN File:

9.675.00

VSAPI OPR PATTERN Date:

23 Jan 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

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
    • {malware file name} = "ODUuMTcuMTMyLjU0OwAA"

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_LOCAL_MACHINE\SOFTWARE\Google\Chrome\Extensions
    • cdjbnddbclciabnckgeahmneohjlahdm

Step 4

Search and delete this file

[ Learn More ]
There may be some files that are hidden. Please make sure you check the Search Hidden Files and Folders checkbox in the "More advanced options" option to include all hidden files and folders in the search result.
  • %AppDataLocal%\chromeupdate.crx

Step 5

Scan your computer with your Trend Micro product to delete files detected as TROJ_MEDFOS.AIJ. 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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