Analysis by: Jasen Sumalapao
ALIASES:

Trojan:Win32/Medfos.B (Microsoft), Trojan.Win32.Powa.eyn (Kaspersky), Trojan.Malcol (Symantec), Medfos.c (NAI), Mal/Medfos-C (Sophos), Gen:Variant.Kazy.64219 (FSecure), Trojan.Win32.Generic!BT (Sunbelt), TR/Crypt.ZPACK.Gen8 (Antivir), W32/Medfos.B.gen!Eldorado (Authentium), Gen:Variant.Kazy.64219 (Bitdefender), W32/DxBDWV!tr (Fortinet), W32/Medfos.B.gen!Eldorado (generic, not disinfectable) (Fprot), Win32.SuspectCrc (Ikarus), a variant of Win32/Medfos.J trojan (NOD32)

 PLATFORM:

Windows 2000, Windows XP, Windows Server 2003

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

  • Threat Type: Trojan

  • Destructiveness: No

  • Encrypted: Yes

  • In the wild: Yes

  OVERVIEW

Infection Channel: Dropped by other malware, Downloaded from the Internet

This Trojan may arrive bundled with malware packages as a malware component. It may arrive as a file that exports functions used by other malware. It arrives on a system as a file dropped by other malware or as a file downloaded unknowingly by users when visiting malicious sites.

It creates folders where it drops its files.

It displays advertisements on Internet browsers.

It requires its main component to successfully perform its intended routine. It redirects browsers to certain sites. It presents itself as a plugin/add-on/extension for certain applications. It executes certain actions WITHIN the affected computer.

  TECHNICAL DETAILS

File Size: 237,568 bytes
Memory Resident: Yes
Initial Samples Received Date: 21 May 2012
Payload: Connects to URLs/IPs, Displays ads, Downloads files

Arrival Details

This Trojan may arrive bundled with malware packages as a malware component.

It may arrive as a file that exports functions used by other malware.

It 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 Trojan drops the following component file(s):

  • %Application Data%\{BB07A295-7B79-11E1-826D-B8AC6F996F26}\chrome\content\browser.xul - detected as JS_MEDFOS.EXT
  • %Application Data%\{BB07A295-7B79-11E1-826D-B8AC6F996F26}\chrome.manifest
  • %Application Data%\{BB07A295-7B79-11E1-826D-B8AC6F996F26}\install.rdf

(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%\{BB07A295-7B79-11E1-826D-B8AC6F996F26}
  • %Application Data%\{BB07A295-7B79-11E1-826D-B8AC6F996F26}\chrome
  • %Application Data%\{BB07A295-7B79-11E1-826D-B8AC6F996F26}\chrome\content

(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.)

Other System Modifications

This Trojan adds the following registry entries:

HKEY_CURRENT_USER\Software\Mozilla\
Firefox\Extensions
{BB07A295-7B79-11E1-826D-B8AC6F996F26} = %Application Data%\{BB07A295-7B79-11E1-826D-B8AC6F996F26}\

Adware Routine

This Trojan displays advertisements on Internet browsers.

Other Details

This Trojan requires its main component to successfully perform its intended routine.

It redirects browsers to the following sites:

  • {BLOCKED}ppcfeed.com

It presents itself as a plugin/add-on/extension for the following applications:

  • Translate This! 2.0 for Mozilla Firefox

It executes the following:

  • Download and execute other malware
  • Modify browser's settings and initializations

NOTES:
This Trojan uses the following format for redirection:

  • http://{redirected URL}/feed?type=live&ua=MSIE

  SOLUTION

Minimum Scan Engine: 9.200
FIRST VSAPI PATTERN FILE: 9.130.06
FIRST VSAPI PATTERN DATE: 23 May 2012
VSAPI OPR PATTERN File: 9.131.00
VSAPI OPR PATTERN Date: 24 May 2012

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

Remove malware/grayware files dropped/downloaded by TROJ_MEDFOS.SMB

    • JS_MEDFOS.EXT

Step 3

Restart in Safe Mode

[ Learn More ]

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\Mozilla\Firefox\Extensions
    • {BB07A295-7B79-11E1-826D-B8AC6F996F26} = %Application Data%\{BB07A295-7B79-11E1-826D-B8AC6F996F26}\

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%\{BB07A295-7B79-11E1-826D-B8AC6F996F26}

Step 6

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


Did this description help? Tell us how we did.