BKDR_SCAR.TU

 Analysis by: Kathleen Notario
 Modified by: Sabrina Lei Sioting

 ALIASES:

Trojan.Gen (Symantec); Trojan.Win32.Scar.enhg (Kaspersky)

 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 runs certain commands that it receives remotely from a malicious user. Doing this puts the affected computer and information found on the computer at greater risk. It connects to a website to send and receive information.

It deletes the initially executed copy of itself.

  TECHNICAL DETAILS

File Size:

110,592 bytes

File Type:

EXE

Memory Resident:

Yes

Initial Samples Received Date:

13 Sep 2011

Payload:

Connects to URLs/IPs

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.

Installation

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

  • %Program Files%\NetServices\Schied.exe

(Note: %Program Files% is the default Program Files folder, usually C:\Program Files.)

It creates the following folders:

  • %Program Files%\NetServices

(Note: %Program Files% is the default Program Files folder, usually C:\Program Files.)

Autostart Technique

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

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Active Setup\Installed Components\{A0XC6A98-A14C-J35H-46UD-F5AR862J2AH5}
StubPath = "%Program Files%\NetServices\Schied.exe"

Other System Modifications

This backdoor adds the following registry keys as part of its installation routine:

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Active Setup\Installed Components\{A0XC6A98-A14C-J35H-46UD-F5AR862J2AH5}

Backdoor Routine

This backdoor executes the following command(s) from a remote malicious user:

  • Execute command shell (cmd.exe)
  • Execute process
  • Log keystrokes
  • Retrieve system information

It connects to the following websites to send and receive information:

  • http://{BLOCKED}nny2017.rr.nu/mail.asp
  • http://{BLOCKED}.sitelutions.com

Other Details

This backdoor deletes the initially executed copy of itself

NOTES:

This malware also connects to the aforementioned URLs to report system infection and to send system information such as the following:

  • Host name
  • OS version
  • User name
  • Volume information

  SOLUTION

Minimum Scan Engine:

9.200

VSAPI OPR PATTERN File:

8.425.00

VSAPI OPR PATTERN Date:

13 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

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. Before you could do this, you must restart in Safe Mode. For instructions on how to do this, you may refer to this page If the preceding step requires you to restart in safe mode, you may proceed to edit the system registry.

  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Active Setup\Installed Components
    • {A0XC6A98-A14C-J35H-46UD-F5AR862J2AH5}

Step 4

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.
  • %Program Files%\NetServices

Step 5

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