Analysis by: Marvelous Pelin
ALIASES:

HEUR:Trojan-Ransom.OSX.Crypat.a(Kaspersky)

 PLATFORM:

Mac OS

 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

Payload: 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:

  • /Documents/README!.txt - ransom note
  • /Downloads/README!.txt - ransom note
  • /Movies/README!.txt - ransom note
  • /Pictures/README!.txt - ransom note
  • /Music/README!.txt - ransom note
  • /Public/README!.txt - ransom note
  • /Desktop/README.txt - ransom note
  • /Desktop/HOW_TO_DECRYPT.txt - ransom note
  • /Desktop/DECRYPT.txt - ransom note

Other Details

This Trojan renames encrypted files using the following names:

  • {original filename and extension}.crypt

It does the following:

  • The ransomware encrypts files located in the following locations:
    • /Users/
    • /Volumes/
  • It executes the /usr/bin/diskutil with the following parameters to overwrite free space and prevent file recovery:
    • secureErase
    • freespace
  • It modifies the timestamp of the encrypted files to "February 13, 2010".

NOTES:

The ransom note shows the following:

  SOLUTION

Minimum Scan Engine: 9.850
FIRST VSAPI PATTERN FILE: 13.242.00
FIRST VSAPI PATTERN DATE: 24 Feb 2017
VSAPI OPR PATTERN File: 13.243.00
VSAPI OPR PATTERN Date: 25 Feb 2017

Step 1

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 2

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.  
  • /Documents/README!.txt /Downloads/README!.txt
  • /Movies/README!.txt
  • /Pictures/README!.txt
  • /Music/README!.txt
  • /Public/README!.txt
  • /Desktop/README.txt
  • /Desktop/HOW_TO_DECRYPT.txt
  • /Desktop/DECRYPT.txt

Step 3

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

Step 4

Restore encrypted files from backup.


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