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BKDR_SHELL.NLT

August 19, 2013
 Analysis by: Nikko Tamana
 PLATFORM:

Windows 2000, Windows Server 2003, Windows XP (32-bit, 64-bit), Windows Vista (32-bit, 64-bit), Windows 7 (32-bit, 64-bit)

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

  • Threat Type: Backdoor

  • Destructiveness: No

  • Encrypted: Yes

  • In the wild: Yes

  OVERVIEW

Infection Channel:

Downloaded from the Internet, Dropped by other malware

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 downloaded by other malware/grayware from remote sites.

It does not have any propagation routine.

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

It does not have any downloading capability.

  TECHNICAL DETAILS

File Size:

63,488 bytes

File Type:

EXE

Memory Resident:

Yes

Initial Samples Received Date:

13 Aug 2013

Payload:

Compromises system security, Connects to URLs/IPs, Collects system information, Steals information

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 downloaded by the following malware/grayware from remote sites:

  • LNK_DLOADR.ILP

Installation

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

  • %All Users Profile%\intel.exe
  • %System Root%\Users\All Users\intel.exe - Windows Vista or 7

(Note: %All Users Profile% is the All Users or Common profile folder, which is C:\Documents and Settings\All Users in Windows 2000, XP, and Server 2003, and C:\ProgramData in Windows Vista and 7.. %System Root% is the root folder, which is usually C:\. It is also where the operating system is located.)

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

  • PST-2.0

Other System Modifications

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

HKEY_CLASSES_ROOT\LOG
CLSID = "{hex values}"

HKEY_LOCAL_MACHINE\SOFTWARE\Classes\
LOG
CLSID = "{hex values}"

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\Run
intel = ""

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

HKEY_CLASSES_ROOT\LOG

HKEY_CLASSES_ROOT\LOGPROXY

HKEY_LOCAL_MACHINE\SOFTWARE\Classes\
LOG

HKEY_LOCAL_MACHINE\SOFTWARE\Classes\
LOGPROXY

Propagation

This backdoor does not have any propagation routine.

Backdoor Routine

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

  • Perform remote shell execution
  • File management
  • Create directories
  • Get drive information
  • Get processor information
  • Screen capture

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

  • http://{BLOCKED}se.{BLOCKED}tingrecovery.net/{random hex values}FFFFFFFF.aspx

Download Routine

This backdoor does not have any downloading capability.

Information Theft

This backdoor gathers the following data:

  • Computer Name
  • OECMP
  • User Name

NOTES:

It disables the firewall by executing in command prompt the line net stop SharedAccess.

It does not have rootkit capabilities.

It does not exploit any vulnerability.

  SOLUTION

Minimum Scan Engine:

9.300

FIRST VSAPI PATTERN FILE:

10.216.08

FIRST VSAPI PATTERN DATE:

14 Aug 2013

VSAPI OPR PATTERN File:

10.217.00

VSAPI OPR PATTERN Date:

15 Aug 2013

Step 1

Before doing any scans, Windows XP, Windows Vista, and Windows 7 users must disable System Restore to allow full scanning of their computers.

Step 2

Remove malware/grayware files that dropped/downloaded BKDR_SHELL.NLT

  • LNK_DLOADR.ILP

Step 3

Restart in Safe Mode

[ Learn More ]

Step 4

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_CLASSES_ROOT
    • LOG
  • In HKEY_CLASSES_ROOT
    • LOGPROXY
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Classes
    • LOG
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Classes
    • LOGPROXY

Step 5

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_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Run
    • intel = ""

Step 6

Search and delete these files

[ 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.
  • %All Users Profile%\intel.exe
  • %System Root%\Users\All Users\intel.exe - Windows Vista or 7

Step 7

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