JS_SHELLRAT.A

April 19, 2015
 Analysis by: Abraham Latimer Camba
 PLATFORM:

Windows

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

  • Threat Type: Backdoor

  • Destructiveness: No

  • Encrypted: No

  • In the wild: Yes

  OVERVIEW

Infection Channel:

Dropped by other malware

This backdoor may be dropped by other malware.

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

It deletes itself after execution.

  TECHNICAL DETAILS

File Size:

17,149 bytes

File Type:

JS

Memory Resident:

Yes

Initial Samples Received Date:

17 Apr 2015

Payload:

Connects to URLs/IPs, Compromises system security

Arrival Details

This backdoor may be dropped by the following malware:

Installation

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

  • %Application Data%\Microsoft\Network\network.js

(Note: %Application Data% is the Application Data folder, where it usually is C:\Documents and Settings\{user name}\Application Data on Windows 2000, Windows Server 2003, and Windows XP (32- and 64-bit); C:\Users\{user name}\AppData\Roaming on Windows Vista (32- and 64-bit), Windows 7 (32- and 64-bit), Windows 8 (32- and 64-bit), Windows 8.1 (32- and 64-bit), Windows Server 2008, and Windows Server 2012.)

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
network = "wscript.exe "%Application Data%\Microsoft\Network\network.js""

Backdoor Routine

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

  • Directory
    • Create directories
    • Delete directories
  • GetFiles
    • Enumerate files
  • File
    • Copy files
    • Delete files
    • Read files
    • Modify files
  • GetFileInfo
    • Get file information (size, date created, date last accessed, date last modified)
  • Network
    • Perform an HTTP GET request on a specified URL
  • Process
    • Create processes
    • Kill processes
    • List processes
    • Run files
  • Reg
    • Delete registry entries
    • Read registry entries
    • Modify registry entries
  • System
    • Enumerate drives and get drive information (file system, total space, free space)
    • Get current user's security identifier (SID)
  • Time
    • Get current time
  • Download files from a specified URL
  • Execute javascript received from C&C

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

  • http://{BLOCKED}ays.mooo.com/common.php

It posts the following information to its command and control (C&C) server:

  • Volume serial number of logical disk
  • IP address
  • OS version
  • Proxy server
  • Computer name
  • Current user name

Other Details

This backdoor deletes itself after execution.

  SOLUTION

Minimum Scan Engine:

9.750

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

Note that not all files, folders, and registry keys and entries are installed on your computer during this malware's/spyware's/grayware's execution. This may be due to incomplete installation or other operating system conditions. If you do not find the same files/folders/registry information, please proceed to the next step.

Step 3

Remove the malware/grayware file that dropped/downloaded JS_SHELLRAT.A. (Note: Please skip this step if the threat(s) listed below have already been removed.)

Step 4

Restart in Safe Mode

[ Learn More ]

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_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Run
    • network = "wscript.exe "%Application Data%\Microsoft\Network\network.js""

Step 6

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