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RANSOM_CRIPTOSO.A

May 19, 2016
 Analysis by: Jennifer Gumban
 PLATFORM:

Windows

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

  • Threat Type: Trojan

  • Destructiveness: No

  • Encrypted:

  • In the wild: Yes

  OVERVIEW

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

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.

It may be downloaded from the following remote sites:

  • http://{BLOCKED}ome69.com/2/booyah.exe

Installation

This Trojan drops the following files:

  • {folders containing encrypted files}\CRIPTOSO.KEY
  • %Application Data%\{8 numbers} - contains the list of files encrypted
  • {folders containing encrypted files}\WHATHAPPENDTOYOURFILES.TXT - ransomnote

(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.)

File Infection

This Trojan avoids infecting folders containing the following strings:

  • gamemedia
  • application
  • system
  • compressed
  • video
  • text
  • document
  • audio
  • image

Other Details

This Trojan encrypts files with the following extensions:

  • .mht
  • .zip
  • .dvr-ms
  • .wvx
  • .wmx
  • .wmv
  • .wm
  • .mpv2
  • .mpg
  • .mpeg
  • .mpe
  • .mpa
  • .mp2v
  • .mp2
  • .m1v
  • .IVF
  • .asx
  • .asf
  • .wax
  • .snd
  • .rmi
  • .m3u
  • .au
  • .aiff
  • .aifc
  • .aif
  • .midi
  • .mid
  • .wma
  • .wav
  • .mp3
  • .wmf
  • .tiff
  • .tif
  • .rle
  • .png
  • .jpeg
  • .jpe
  • .jpg
  • .jfif
  • .ico
  • .gif
  • .emf
  • .dib
  • .bmp
  • .docx
  • .pptx
  • .pptx
  • .xlsx
  • .xlsx
  • .xbap
  • .xbap
  • .xps
  • .xps
  • .pdf
  • .pdf
  • .pot
  • .pot
  • .hta
  • .xlt
  • .xlt
  • .pps
  • .pps
  • .xlw
  • .xlw
  • .dot
  • .dot
  • .rtf
  • .rtf
  • .ppt
  • .ppt
  • .xls
  • .xls
  • .doc
  • .doc
  • .xml
  • .xml
  • .htm
  • .html
  • .html
  • .htm
  • .hta

It does the following:

  • It displays the ff. ransomnote:

    Your ID: {8 numbers}
    * * *
    Hi. Your files are now encrypted. I have the key to decrypt them back.
    I will give you a decrypter if you pay me.
    If you pay me today, the price is only 1 bitcoin.
    If you pay me tomorrow, you will have to pay 2 bitcoins.
    If you pay me one week later the price will be 7 bitcoins and so on. So, hurry up.

    Contact me using this email address: mohammad@opensourcemail.org

Mobile Malware Routine

This Trojan accesses the following website(s) to send and receive information:

  • http://{BLOCKED}rome69.com/knock.php?id=758275

  SOLUTION

Minimum Scan Engine:

9.800

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

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

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.  
  • CRIPTOSO.KEY
  • %Application Data%\{8 numbers}
  • WHATHAPPENDTOYOURFILES.TXT

Step 5

Restore encrypted files from backup.


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