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TROJ_STASER.AN

October 12, 2013
 ALIASES:

Trojan.Win32.Staser.rnk (Kaspersky); Trojan horse BackDoor.Agent.AWCG (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:

105,041,920 bytes

File Type:

EXE

Memory Resident:

Yes

Initial Samples Received Date:

12 Oct 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:

  • %Program Files%\Windows Howzfu\Opuymmu.exe

(Note: %Program Files% is the default Program Files folder, usually C:\Program Files in Windows 2000, Server 2003, and XP (32-bit), Vista (32-bit), and 7 (32-bit), or C:\Program Files (x86) in Windows XP (64-bit), Vista (64-bit), and 7 (64-bit).)

It creates the following folders:

  • %Program Files%\Windows Howzfu

(Note: %Program Files% is the default Program Files folder, usually C:\Program Files in Windows 2000, Server 2003, and XP (32-bit), Vista (32-bit), and 7 (32-bit), or C:\Program Files (x86) in Windows XP (64-bit), Vista (64-bit), and 7 (64-bit).)

Autostart Technique

This Trojan registers as a system service to ensure its automatic execution at every system startup by adding the following registry keys:

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\Wsbqco qucuqymv

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\Ieeugs nggfgi

Other System Modifications

This Trojan adds the following registry keys:

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Control\MediaResources\msvideo

It adds the following registry entries:

HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\
Services\Wsbqco qucuqymv
ReleiceName = "Ieeugs nggfgi"

HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\
Services\Ieeugs nggfgi
ConnectGroup = "È⼦"

HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\
Services\Ieeugs nggfgi
MarkTime = "2013-10-03 00:40"

HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\
Services\Ieeugs nggfgi
Description = "Bfdwca crkaymmi fciwtsgguxa"

Dropping Routine

This Trojan drops the following files:

  • %System Root%\1280.vbs

(Note: %System Root% is the root folder, which is usually C:\. It is also where the operating system is located.)

Other Details

This Trojan 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\SYSTEM\CurrentControlSet\Services
    • Wsbqco qucuqymv
  • In HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services
    • Ieeugs nggfgi
  • In HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\MediaResources
    • msvideo

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\SYSTEM\ControlSet001\Services\Wsbqco qucuqymv
    • ReleiceName = "Ieeugs nggfgi"
  • In HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\Services\Ieeugs nggfgi
    • ConnectGroup = "È⼦"
  • In HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\Services\Ieeugs nggfgi
    • MarkTime = "2013-10-03 00:40"
  • In HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\Services\Ieeugs nggfgi
    • Description = "Bfdwca crkaymmi fciwtsgguxa"

Step 5

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.
  • %System Root%\1280.vbs

Step 6

Search and delete this folder

[ 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.
  • %Program Files%\Windows Howzfu

Step 7

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