Analysis by: Sabrina Lei Sioting
 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 is related to a possible targeted attack.

This backdoor arrives as an attachment to email messages spammed by other malware/grayware or malicious users. It may be dropped by other malware.

It executes commands from a remote malicious user, effectively compromising the affected system.

  TECHNICAL DETAILS

File Size: 19,968 bytes
File Type: EXE
Memory Resident: Yes
Initial Samples Received Date: 02 Sep 2011

Arrival Details

This backdoor arrives as an attachment to email messages spammed by other malware/grayware or malicious users.

It may be dropped by the following malware:

  • TROJ_DROPPER.TKD

Autostart Technique

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

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Run
{malware name} = "{malware path}\{malware name}.exe "

Backdoor Routine

This backdoor executes the following commands from a remote malicious user:

  • /put
  • /run
  • /sleep
  • cmd /c command
  • help:

It connects to the following URL(s) to send and receive commands from a remote malicious user:

  • http://{BLOCKED}b.linkin.tw/AWS96.jsp?{random characters}

Other Details

This backdoor connects to the following URL(s) to check for an Internet connection:

  • www.google.com.tw

  SOLUTION

Minimum Scan Engine: 9.200
FIRST VSAPI PATTERN FILE: 8.396.08
FIRST VSAPI PATTERN DATE: 02 Sep 2011
VSAPI OPR PATTERN File: 8.397.00
VSAPI OPR PATTERN Date: 03 Sep 2011

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 the malware/grayware file that dropped/downloaded BKDR_SMALL.NAE

Step 3

Identify and terminate files detected as BKDR_SMALL.NAE

[ 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\CurrentVersion\Run
    • {malware name} = {malware path}\{malware name}.exe

Step 5

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