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TROJ_AGENT.SXX

June 07, 2013
 ALIASES:

Downloader-AWE (McAfee); Downloader (Symantec); Trojan-Downloader.Win32.Agent.aqr (Kaspersky); BehavesLike.Win32.Malware.ssc (mx-v) (Sunbelt); Trojan horse Downloader.Agent.FHO (AVG)

 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.

It deletes itself after execution.

  TECHNICAL DETAILS

File Size:

31,744 bytes

File Type:

EXE

Memory Resident:

Yes

Initial Samples Received Date:

07 Jun 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.

Installation

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

  • %System%\Realplayer.exe

(Note: %System% is the Windows system folder, which is usually C:\Windows\System32.)

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
Realplayer.exe = "%System%\Realplayer.exe"

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Run
Realplayer.exe = "%System%\Realplayer.exe"

Other System Modifications

This Trojan adds the following registry keys:

HKEY_LOCAL_MACHINE\Software\Microsoft\
Baidu\info

HKEY_LOCAL_MACHINE\Software\Microsoft NT\
Windows\CurrentVersion\Winlogon

It adds the following registry entries:

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Baidu\info
h123 = "0"

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft NT\
Windows\CurrentVersion\Winlogon
Shell = "Explorer.exe %System%\Realplayer.exe"

Dropping Routine

This Trojan drops the following files:

  • %Windows%\gafsdaz.bat
  • %System%\Rsvtub.dll
  • %Windows%\gnimatmd.bat
  • %User Temp%\v20060903.rar
  • %Windows%\v20060903.rar

(Note: %Windows% is the Windows folder, which is usually C:\Windows.. %System% is the Windows system folder, which is usually C:\Windows\System32.. %User Temp% is the current user's Temp folder, which is usually C:\Documents and Settings\{user name}\Local Settings\Temp on Windows 2000, XP, and Server 2003, or C:\Users\{user name}\AppData\Local\Temp on Windows Vista and 7.)

Other Details

This Trojan connects to the following possibly malicious URL:

  • http://update.{BLOCKED}h.com//command0903.html
  • http://l.{BLOCKED}m.com/0903.html

It deletes itself after execution.

This report is generated via an automated analysis system.

  SOLUTION

Minimum Scan Engine:

9.300

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 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\Baidu
    • info
  • In HKEY_LOCAL_MACHINE\Software\Microsoft NT\Windows\CurrentVersion
    • Winlogon

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_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Run
    • Realplayer.exe = "%System%\Realplayer.exe"
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Run
    • Realplayer.exe = "%System%\Realplayer.exe"
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Baidu\info
    • h123 = "0"
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft NT\Windows\CurrentVersion\Winlogon
    • Shell = "Explorer.exe %System%\Realplayer.exe"

Step 5

Search and delete these components

[ Learn More ]
There may be some components 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%\gafsdaz.bat
  • %System%\Rsvtub.dll
  • %Windows%\gnimatmd.bat
  • %User Temp%\v20060903.rar
  • %Windows%\v20060903.rar

Step 6

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