TROJ_AGENT.VBS

October 12, 2012
 ALIASES:

Trojan:Win32/Fotomoto.A (Microsoft); AdClicker-FK (McAfee); Trojan.Vundo (Symantec); Trojan.Win32.Agent.aoy (Kaspersky); Trojan.Win32.Generic!BT (Sunbelt); Trojan.Fotomoto.A (FSecure)

 PLATFORM:

Windows 2000, Windows XP, Windows Server 2003

 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:

122,944 bytes

File Type:

EXE

Memory Resident:

No

Initial Samples Received Date:

16 Nov 2011

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\Microsoft\
DomainService

It adds the following registry entries:

HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\
Services\SharedAccess\Parameters\
FirewallPolicy\StandardProfile\AuthorizedApplications\
List
{malware path and file name} = "{malware path and file name}:*:enabled:xxx"

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
DomainService
next_url_post_time = 4ec3cc9

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
DomainService
installation_id = "00708b79215c70bb49787f093f5d14222684132a"

It modifies the following registry entries:

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows NT\CurrentVersion\Winlogon
SFCDisable = 4

(Note: The default value data of the said registry entry is 0.)

Dropping Routine

This Trojan drops the following files:

  • %Temp%\ssk.
  • %Temp%\ssk.1
  • %Temp%\ssk.2

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

Other Details

This Trojan connects to the following possibly malicious URL:

  • http://{BLOCKED}.141.185/cgi-bin/install.php?{random characters}

This report is generated via an automated analysis system.

  SOLUTION

Minimum Scan Engine:

9.200

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

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\Microsoft
    • DomainService

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\SYSTEM\ControlSet001\Services\SharedAccess\Parameters\FirewallPolicy\StandardProfile\AuthorizedApplications\List
    • {malware path and file name}="{malware path and file name}:*:enabled:xxx"
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\DomainService
    • next_url_post_time=4ec3cc9
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\DomainService
    • installation_id="00708b79215c70bb49787f093f5d14222684132a"

Step 4

Restore this modified 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 NT\CurrentVersion\Winlogon
    • From: SFCDisable=4
      To: SFCDisable=0

Step 5

Search and delete these files

[ 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.
  • %Temp%\ssk.
  • %Temp%\ssk.1
  • %Temp%\ssk.2

Step 6

Scan your computer with your Trend Micro product to delete files detected as TROJ_AGENT.VBS. 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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