BKDR_SMALL.NVZ

 Analysis by: jasperm
 Modified by: MarfelTi

 ALIASES:

Microsoft: Trojan:Win32/Sisproc ; Kaspersky: Trojan.Win32.Genome.kufo

 PLATFORM:

Windows 2000, Windows XP, Windows Server 2003

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

  • Threat Type: Backdoor

  • Destructiveness: No

  • Encrypted: No

  • In the wild: Yes

  OVERVIEW

This backdoor arrives on a system as a file dropped by other malware or as a file downloaded unknowingly by users when visiting malicious sites. It may be dropped by other malware.

It connects to a website to send and receive information.

It deletes the initially executed copy of itself.

  TECHNICAL DETAILS

File Size:

14,332 bytes

File Type:

EXE

Memory Resident:

Yes

Initial Samples Received Date:

22 Sep 2010

Arrival Details

This backdoor arrives on a system as a file dropped by other malware or as a file downloaded unknowingly by users when visiting malicious sites.

It may be dropped by the following malware:

  • TROJ_MDROP.SME

Installation

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

  • %User Temp%\logs\sqlservr.exe

(Note: %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.)

It creates the following folders:

  • %User Temp%\logs

(Note: %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.)

It adds the following mutexes to ensure that only one of its copies runs at any one time:

  • milestone374.dyndns.org:80-1.20

It terminates the execution of the copy it initially executed and executes the copy it drops instead.

Autostart Technique

This backdoor adds the following registry entries to enable its automatic execution at every system startup:

HKEY_CURRENT_USER\Software\Microsoft\
Windows NT\CurrentVersion\Windows
Load = %User Temp%\logs\sqlservr.exe

It drops the following file(s) in the Windows Startup folder to enable its automatic execution at every system startup:

  • Update.bat - batch file which adds an autostart registry entry for the malware

Backdoor Routine

This backdoor connects to the following websites to send and receive information:

  • {BLOCKED}one374.dyndns.org
  • {BLOCKED}321.dyndns.org

Other Details

This backdoor deletes the initially executed copy of itself

NOTES:
It may gather the following information:

  • OS Version
  • ComputerName
  • Information Virtual Memory
  • UserName System

  SOLUTION

Minimum Scan Engine:

8.900

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 BKDR_SMALL.NVZ

    TROJ_MDROP.SME

Step 3

Identify and terminate files detected as BKDR_SMALL.NVZ

[ Learn More ]
  1. If the detected file is displayed in either Windows Task Manager or Process Explorer but you cannot delete it, restart your computer in safe mode. To do this, refer to this link for the complete steps.
  2. If the detected file is not displayed in either Windows Task Manager or Process Explorer, continue doing the next steps.

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_CURRENT_USER\Software\Microsoft\Windows NT\CurrentVersion\Windows
    • Load = %User Temp%\logs\sqlservr.exe

Step 5

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. %User Temp%\logs

Step 6

Search and delete this file

[ 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. Ͽer StartupϿpdate.bat

Step 7

Scan your computer with your Trend Micro product to delete files detected as BKDR_SMALL.NVZ. 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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