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RANSOM_COMCIRCLE.A

February 22, 2017
 Analysis by: Julie Anne Cabuhat
 ALIASES:

Ransom.FileCryptor (Malwarebytes), Win32.Trojan.Crypmodadv.Gvm (Tencent), Trojan:Win32/Dynamer!ac (Microsoft)

 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:

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:

386,560 bytes

File Type:

EXE

Memory Resident:

Yes

Initial Samples Received Date:

08 Oct 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 and executes the following files:

  • %User Temp%\1.exe - screen locker

(Note: %User Temp% is the user's temporary folder, where it usually is C:\Documents and Settings\{user name}\Local Settings\Temp on Windows 2000, Windows Server 2003, and Windows XP (32- and 64-bit); C:\Users\{user name}\AppData\Local\Temp 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.)

Dropping Routine

This Trojan drops the following files:

  • {folder of encrypted files}\RESTORE-FILES!{random numbers}.txt - ransom note

Other Details

This Trojan encrypts files with the following extensions:

  • .vb
  • .scr
  • .reg
  • .pif
  • .msi
  • .lnk
  • .cpl
  • .com
  • .cmd
  • .bat
  • .bas
  • .docx
  • .pptx
  • .xlsx
  • .xbap
  • .xps
  • .pdf
  • .pot
  • .hta
  • .xlt
  • .pps
  • .xlw
  • .dot
  • .rtf
  • .ppt
  • .xls
  • .doc
  • .xml
  • .html
  • .htm
  • .hta
  • .search-ms
  • .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

It renames encrypted files using the following names:

  • {random characters}.comrade

NOTES:

The ransomware displays the following lock screen during encryption:

After encryption, it opens the following ransom note after restarting the computer:

  SOLUTION

Minimum Scan Engine:

9.850

FIRST VSAPI PATTERN FILE:

12.828.03

FIRST VSAPI PATTERN DATE:

08 Oct 2016

VSAPI OPR PATTERN File:

12.829.00

VSAPI OPR PATTERN Date:

09 Oct 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.  
  • %User Temp%\1.exe
  • {folder of encrypted files}\RESTORE-FILES!{random numbers}.txt

Step 5

Restart in normal mode and scan your computer with your Trend Micro product for files detected as RANSOM_COMCIRCLE.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 6

Restore encrypted files from backup.


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