TROJ_NITOL.AH

October 09, 2012
 Analysis by: Michael Cabel
 PLATFORM:

Windows 2000, Windows XP, Windows 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 arrives on a system as a file dropped by other malware or as a file downloaded unknowingly by users when visiting malicious sites.

It connects to certain URLs. It may do this to remotely inform a malicious user of its installation. It may also do this to download possibly malicious files onto the computer, which puts the computer at a greater risk of infection by other threats. As of this writing, the said sites are inaccessible.

  TECHNICAL DETAILS

File Size:

38,912 bytes

Memory Resident:

Yes

Initial Samples Received Date:

10 Feb 2012

Payload:

Downloads files

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:

  • %Windows%\(Random File Name}.exe

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

Autostart Technique

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

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\DSLsevverxsm
Type = "10"

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\DSLsevverxsm
Start = "2"

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\DSLsevverxsm
ErrorControl = "0"

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\DSLsevverxsm
ImagePath = "%Windows%\(Random File Name}.exe"

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\DSLsevverxsm
DisplayName = "DCOM Servervfm Process Launcher."

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\DSLsevverxsm
ObjectName = "LocalSystem"

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\DSLsevverxsm
Description = "DCOM Serversir Process Launcher.."

Download Routine

This Trojan connects to the following malicious URLs:

  • {BLOCKED}8.net:6032

It saves the files it downloads using the following names:

  • stf{Random Characters}.exe

As of this writing, the said sites are inaccessible.

NOTES:
This Trojan sends the following system information to the URL {BLOCKED}8.net:6032:

  • CPU Speed
  • Operating System used
  • RAM
  • System Language

  SOLUTION

Minimum Scan Engine:

9.200

FIRST VSAPI PATTERN FILE:

8.768.02

FIRST VSAPI PATTERN DATE:

10 Feb 2012

VSAPI OPR PATTERN File:

8.769.00

VSAPI OPR PATTERN Date:

11 Feb 2012

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

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
    • DSLsevverxsm

Step 4

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