Analysis by: Michael Cabel
 PLATFORM:

Windows 2000, XP, 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 may be dropped by other malware.

It executes then deletes itself afterward.

It opens random ports.

  TECHNICAL DETAILS

File Size: Varies
File Type: PE
Memory Resident: Yes
Initial Samples Received Date: 01 Sep 2010
Payload: Connects to URLs/Ips

Arrival Details

This backdoor may be dropped by the following malware:

  • TROJ_PDFKA.IO
  • TROJ_MDROPPR.JON

Installation

This backdoor drops the following file(s)/component(s):

  • %Application Data%\Microsoft\ico.exe - also detected as BKDR_SCROG.OK

(Note: %Application Data% is the current user's Application Data folder, which is usually C:\Windows\Profiles\{user name}\Application Data on Windows 98 and ME, C:\WINNT\Profiles\{user name}\Application Data on Windows NT, and C:\Documents and Settings\{user name}\Local Settings\Application Data on Windows 2000, XP, and Server 2003.)

It executes then deletes itself afterward.

Autostart Technique

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

HKEY_CURRENT_USER
ico = %Application Data%\\Microsoft\\ico.exe

Backdoor Routine

This backdoor opens a random port to allow a remote user to connect to the affected system. Once a successful connection is established, the remote user executes commands on the affected system.

Other Details

Based on analysis of the codes, it has the following capabilities:

  • It opens random port, it connects to the following sites:
  • {BLOCKED}.184.42
  • *{BLOCKED}xuz.com
  • * {BLOCKED}.184.42

  SOLUTION

Minimum Scan Engine: 8.900
VSAPI OPR PATTERN File: 07.428.06
VSAPI OPR PATTERN Date: 01 Sep 2010

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_SCROG.OK

  • TROJ_PDFKA.IO
  • TROJ_MDROPPR.JON
    •

Step 3

Terminate a process file/s detected as BKDR_SCROG.OK

[ Learn More ]

*Note: If the detected file/s is/are not displayed in theWindows Task Manager, 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
    • ico = %Application Data%\Microsoft\ico.exe

Step 5

Scan your computer with your Trend Micro product to delete files detected as BKDR_SCROG.OK. 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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