Analysis by: Christopher Daniel So
ALIASES:

Trojan.Win32.VBKrypt.bcuv (Kaspersky), Win32/Fbphotofake.A worm (Nod32), TR/Dropper.Gen (AntiVir), Email-Worm.Win32.Joleee (Ikarus)

 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: Sends messages to the friends of Facebook or Twitter users in an infected computer

It sends messages to the friends of Facebook or Twitter users in an infected computer containing a link to a website hosting the malware TROJ_VBKRYPT.CB.

This Trojan may be downloaded by other malware/grayware from remote sites.

It uses Windows Task Scheduler to create a scheduled task that executes the dropped copy.

  TECHNICAL DETAILS

File Size: Varies
File Type: PE
Memory Resident: Yes
Initial Samples Received Date: 10 Feb 2011

Arrival Details

This Trojan may be downloaded by the following malware/grayware from remote sites:

  • TROJ_VBKRYPT.CB

It may be downloaded from the following remote sites:

  • http://{BLOCKED}0.com/abc/load.php?file=0
  • http://{BLOCKED}0.com/abc/load.php?file=1
  • http://{BLOCKED}0.com/abc/load.php?file=2

Installation

This Trojan drops the following copies of itself into the affected system:

  • %User Profile%\Application Data\{random file name}.exe

(Note: %User Profile% is the current user's profile folder, which is usually C:\Windows\Profiles\{user name} on Windows 98 and ME, C:\WINNT\Profiles\{user name} on Windows NT, and C:\Documents and Settings\{user name} on Windows 2000, XP, and Server 2003.)

It drops the following component file(s):

  • %Windows%\Tasks\fbagent.job - the Scheduled Task file

(Note: %Windows% is the Windows folder, which is usually C:\Windows or C:\WINNT.)

It uses Windows Task Scheduler to create a scheduled task that executes the dropped copy.

Autostart Technique

This Trojan adds the following registry entries to enable its automatic execution at every system startup:

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\Run
{random file name}.exe = "%User Profile%\Application Data\{random file name}.exe"

The scheduled task executes the malware every:

  • Logon

Other System Modifications

This Trojan adds the following registry keys:

HKEY_LOCAL_MACHINE\SOFTWARE\facebook

HKEY_LOCAL_MACHINE\SOFTWARE\twitter

Other Details

This Trojan does the following:

  • It sends messages to the friends of Facebook or Twitter users in an infected computer containing a link to a website hosting the malware TROJ_VBKRYPT.CB.

  SOLUTION

Minimum Scan Engine: 8.900
VSAPI PATTERN File: 7.828.12
VSAPI PATTERN Date: 10 Feb 2011
VSAPI PATTERN Date: 2/10/2011 12:00:00 AM

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

Identify and terminate files detected as TROJ_SOCNET.A

[ Learn More ]
  1. If the detected file is displayed in either Windows Task Manager or Process Explorer but you cannot delete it, restart your computer in safe mode. To do this, refer to this link for the complete steps.
  2. If the detected file is not displayed in either Windows Task Manager or Process Explorer, continue doing the next steps.

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_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Run
    • {random file name}.exe=%User Profile%\Application Data\{random file name}.exe

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_LOCAL_MACHINE\SOFTWARE
    • facebook
  • In HKEY_LOCAL_MACHINE\SOFTWARE
    • twitter

Step 5

Search and delete this file

[ Learn More ]
There may be some component 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. %Windows%\Tasks\fbagent.job

Step 6

Scan your computer with your Trend Micro product to delete files detected as TROJ_SOCNET.A. 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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