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TROJ_SASFIS.WE

October 08, 2012
 Analysis by: jont
 PLATFORM:

Windows 2000, XP, Server 2003

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

  • Threat Type: Trojan

  • Destructiveness: No

  • Encrypted: No

  • In the wild: Yes

  OVERVIEW


This Trojan may be dropped by other malware.

However, as of this writing, the said sites are inaccessible.

  TECHNICAL DETAILS

File Size:

21,504 bytes

File Type:

DLL

Memory Resident:

Yes

Initial Samples Received Date:

20 Oct 2010

Arrival Details

This Trojan may be dropped by the following malware:

  • TROJ_BREDLAB.TX

Installation

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

  • %System%\{random filename}

(Note: %System% is the Windows system folder, which is usually C:\Windows\System on Windows 98 and ME, C:\WINNT\System32 on Windows NT and 2000, or C:\Windows\System32 on Windows XP and Server 2003.)

It injects itself into the following processes as part of its memory residency routine:

  • svchost.exe

Autostart Technique

This Trojan modifies the following registry entries to ensure it automatic execution at every system startup:

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows NT\CurrentVersion\Winlogon
Shell = Explorer.exe rundll32.exe {random filename} {random function name}

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

Other System Modifications

This Trojan adds the following registry keys:

HKEY_LOCAL_MACHINE\SOFTWARE\Classes\
idid

Backdoor Routine

However, as of this writing, the said sites are inaccessible.

Other Details

This Trojan connects to the following possibly malicious URL:

  • http://{BLOCKED}viagra.ru/viskas/bb.php
  • http://{BLOCKED}c.ru/mydog/bb.php

  SOLUTION

Minimum Scan Engine:

8.900

VSAPI PATTERN File:

7.552.18

VSAPI PATTERN Date:

20 Oct 2010

VSAPI PATTERN Date:

10/20/2010 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

Remove malware files dropped/downloaded by TROJ_SASFIS.WE

    TROJ_BREDLAB.TX

Step 3

Scan your computer with your Trend Micro product and note files detected as TROJ_SASFIS.WE

Step 4

Restart in Safe Mode

[ Learn More ]

Step 5

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\Classes
    • idid

Step 6

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: Shell = Explorer.exe rundll32.exe {random filename} {random function name}
      To: Explorer.exe

Step 7

Scan your computer with your Trend Micro product to delete files detected as TROJ_SASFIS.WE. 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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