RANSOM_PSHEL.A

 Analysis by: Ryan Gardo

 ALIASES:

PowerShell/Filecoder.K (ESET-NOD32)

 PLATFORM:

Windows

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

  • Threat Type: Trojan

  • Destructiveness: No

  • Encrypted:

  • In the wild: Yes

  OVERVIEW

Infection Channel:

Dropped by other malware, Downloaded from the Internet


This Trojan arrives on a system as a file dropped by other malware or as a file downloaded unknowingly by users when visiting malicious sites.

  TECHNICAL DETAILS

File Size:

32,256 bytes

File Type:

EXE

Memory Resident:

Yes

Initial Samples Received Date:

29 Nov 2016

Payload:

Drops files, Encrypts Files

Arrival Details

This Trojan 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 Trojan drops the following files:

  • %Temp%\drives.csv

(Note: %Temp% is the Windows temporary folder, where it usually is C:\Windows\Temp on all Windows operating system versions.)

Other Details

This Trojan does the following:

  • Encrypts files in the following directories:
    • User Profile
    • Desktop
    • Documents
    • Pictures
    • Downloads

  • Accepts the following commands from the user:
    • -wait
    • -extract [file]
    • -end
    • -debug

  • Skips encrypting the following drives/registries that starts with the following strings:
    • A:
    • B:
    • HKEY

NOTES:

Requires the following certificate to execute its malicious routine:

  • Cert:\CurrentUser\My\A306722ED24C24A21B8A53048BABA8300C192D99
  • Requires Windows Management Framework 3.0 to run as intended.

      SOLUTION

    Minimum Scan Engine:

    9.800

    FIRST VSAPI PATTERN FILE:

    12.930.08

    FIRST VSAPI PATTERN DATE:

    30 Nov 2016

    VSAPI OPR PATTERN File:

    12.931.00

    VSAPI OPR PATTERN Date:

    01 Dec 2016

    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

    Restart in Safe Mode

    [ Learn More ]

    Step 4

    Search and delete this file

    [ Learn More ]
    There may be some 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.  
    • %Temp%\drives.csv

    Step 5

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