Analysis by: David John Agni
ALIASES:

Ransom:Win32/Fortrypt.A (Microsoft), Trojan.CryptoFortress (Malwarebytes)

 PLATFORM:

Windows

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

  • Threat Type: Trojan

  • Destructiveness: No

  • Encrypted: No

  • In the wild: Yes

  OVERVIEW

Infection Channel: Downloaded from the Internet, Dropped by other malware

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: 250,368 bytes
File Type: EXE
Memory Resident: Yes
Initial Samples Received Date: 06 Mar 2015
Payload: Encrypts files, Displays message/message boxes

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

  • Catawba!

Other Details

This Trojan encrypts files with the following extensions:

  • *.0??
  • *.1cd
  • *.3fr
  • *.3gp
  • *.7z
  • *.?ar
  • *.abk
  • *.accdb
  • *.adf
  • *.ai
  • *.arc
  • *.arj
  • *.arw
  • *.ashbak
  • *.ashdisk
  • *.avi
  • *.ba?
  • *.backup
  • *.bk?
  • *.bmp
  • *.bup
  • *.cdr
  • *.cdx
  • *.cer
  • *.cf
  • *.cfu
  • *.cr?
  • *.cs?
  • *.da?
  • *.dbf
  • *.dcr
  • *.der
  • *.dic
  • *.divx
  • *.djvu
  • *.dng
  • *.doc
  • *.doc?
  • *.dt
  • *.dwg
  • *.dx?
  • *.e?f
  • *.efd
  • *.eps
  • *.er?
  • *.fbw
  • *.fh
  • *.flv
  • *.frp
  • *.gh?
  • *.gif
  • *.gzip
  • *.hbi
  • *.hdb
  • *.htm
  • *.html
  • *.ifo
  • *.img
  • *.indd
  • *.iso
  • *.iv2i
  • *.jpeg
  • *.jpg
  • *.kdc
  • *.key
  • *.kwm
  • *.ld?
  • *.m2v
  • *.max
  • *.md
  • *.md?
  • *.mef
  • *.mkv
  • *.mov
  • *.mp4
  • *.mpeg
  • *.mpg
  • *.mrw
  • *.nba
  • *.ndf
  • *.nef
  • *.nr?
  • *.od?
  • *.ol?
  • *.one
  • *.orf
  • *.p12
  • *.p7?
  • *.pb?
  • *.pd?
  • *.pef
  • *.pem
  • *.pfx
  • *.png
  • *.pps
  • *.pps?
  • *.ppt
  • *.ppt?
  • *.psd
  • *.pst
  • *.ptx
  • *.pwm
  • *.qbw
  • *.r??
  • *.sco
  • *.sef
  • *.sk
  • *.sr2
  • *.srf
  • *.srw
  • *.tbk
  • *.tc
  • *.tib
  • *.tif
  • *.tmd
  • *.txt
  • *.v?
  • *.v??
  • *.v???
  • *.wb2
  • *.wbb
  • *.wim
  • *.wmv
  • *.wpd
  • *.wps
  • *.x3f
  • *.xl?
  • *.xls?
  • *.xml
  • *.z?
  • *.z??
  • *.z???

NOTES:

This Trojan drops the file READ IF YOU WANT YOUR FILES BACK.html on all folders it encrypts.

It executes the following command to delete shadow copies:

  • vssadmin delete shadows /all /quiet
  • del /f /q %0

The said .HTML file contains description and instructions on what happened to their files and how to restore them.

Its initial price is 1.43 BTC equivalent to 500 USD and after a couple of days the price is doubled.

It also offers to decrypt two files for free to convince victims that the files can be restored.

  SOLUTION

Minimum Scan Engine: 9.750
FIRST VSAPI PATTERN FILE: 11.522.03
FIRST VSAPI PATTERN DATE: 05 Mar 2015
VSAPI OPR PATTERN File: 11.523.00
VSAPI OPR PATTERN Date: 06 Mar 2015

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

Identify and terminate files detected as TROJ_CRYPFORT.A

[ Learn More ]
  1. Windows Task Manager may not display all running processes. In this case, please use a third-party process viewer, preferably Process Explorer, to terminate the malware/grayware/spyware file. You may download the said tool here.
  2. If the detected file is displayed in either Windows Task Manager or Process Explorer but you cannot delete it, restart your computer in safe mode. To do this, refer to this link for the complete steps.
  3. If the detected file is not displayed in either Windows Task Manager or Process Explorer, continue doing the next steps.

Step 4

Search and delete these files

[ 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.  
  • READ IF YOU WANT YOUR FILES BACK.html

Step 5

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