Analysis by: Ryan Paolo Maglaque
ALIASES:

Ransom:Win32/FileCryptor(Microsoft);W32/Reconyc.HUJZ!tr(Fortinet);a variant of Win32/Filecoder.RozaLocker.A trojan(Eset NOD32);

 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.

It modifies the affected system's HOSTS files. This prevents users from accessing certain websites.

  TECHNICAL DETAILS

File Size: 10,692,096 bytes
Memory Resident: Yes
Initial Samples Received Date: 13 Mar 2017
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 copies of itself into the affected system and executes them:

  • %Windows%\svchost.exe

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

It drops the following files:

  • %Windows%\tr
  • %Windows%\black.bmp

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

It drops and executes the following files:

  • %System Root%\ReadMe.txt

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

Other System Modifications

This Trojan adds the following registry entries as part of its installation routine:

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Policies\
system
DisableTaskMgr = 1

It changes the desktop wallpaper by modifying the following registry entries:

HKEY_CURRENT_USER\Control Panel\Desktop
Wallpaper = %Windows%\black.bmp

(Note: The default value data of the said registry entry is {user preference}.)

It sets the system's desktop wallpaper to the following image:

  • %Windows%\black.bmp

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

HOSTS File Modification

This Trojan adds the following strings to the Windows HOSTS file:

  • 127.0.0.1 http://vk.com
  • 127.0.0.1 http://m.vk.com
  • 127.0.0.1 http://ok.ru
  • 127.0.0.1 http://playground.ru
  • 127.0.0.1 http://stopgame.ru
  • 127.0.0.1 http://ag.ru
  • 127.0.0.1 http://kaspersky.com
  • 127.0.0.1 http://symantec.com
  • 127.0.0.1 http://free.drweb.com
  • 127.0.0.1 http://drweb.com
  • 127.0.0.1 http://free.drweb.ru
  • 127.0.0.1 http://drweb.ru
  • 127.0.0.1 https://vk.com
  • 127.0.0.1 https://m.vk.com
  • 127.0.0.1 https://ok.ru
  • 127.0.0.1 https://playground.ru
  • 127.0.0.1 https://stopgame.ru
  • 127.0.0.1 https://ag.ru
  • 127.0.0.1 https://kaspersky.com
  • 127.0.0.1 https://symantec.com
  • 127.0.0.1 https://free.drweb.com
  • 127.0.0.1 https://drweb.com
  • 127.0.0.1 http://free.drweb.ru
  • 127.0.0.1 https://drweb.ru
  • 127.0.0.1 vk.com
  • 127.0.0.1 m.vk.com
  • 127.0.0.1 ok.ru
  • 127.0.0.1 playground.ru
  • 127.0.0.1 stopgame.ru
  • 127.0.0.1 ag.ru
  • 127.0.0.1 kaspersky.com
  • 127.0.0.1 symantec.com
  • 127.0.0.1 free.drweb.com
  • 127.0.0.1 drweb.com
  • 127.0.0.1 free.drweb.ru
  • 127.0.0.1 drweb.ru

Other Details

This Trojan encrypts files with the following extensions:

  • .a3d
  • .blend
  • .dds
  • .djv
  • .doc
  • .docm
  • .docx
  • .fb2
  • .fb3
  • .jpeg
  • .jpg
  • .lwp
  • .max
  • .obj
  • .ods
  • .odt
  • .pdf
  • .pdn
  • .png
  • .rft
  • .svg
  • .sxc
  • .sxw
  • .unity
  • .xls
  • .xlsm
  • .xlsx

It renames encrypted files using the following names:

  • {Original File Name and Extension}.enc

It does the following:

  • Execute the following command to terminate task manager: "%System%\cmd.exe" /c taskkill /f /im taskmgr.exe
  • It displays the following window:

  • It displays the following Ransom Note:

  SOLUTION

Minimum Scan Engine: 9.850
FIRST VSAPI PATTERN FILE: 13.274.08
FIRST VSAPI PATTERN DATE: 13 Mar 2017
VSAPI OPR PATTERN File: 13.275.00
VSAPI OPR PATTERN Date: 14 Mar 2017

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

Delete this registry value

[ Learn More ]

Important: Editing the Windows Registry incorrectly can lead to irreversible system malfunction. Please do this step only if you know how or you can ask assistance from your system administrator. Else, check this Microsoft article first before modifying your computer's registry.

 
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Policies\system
    • DisableTaskMgr = 1

Step 5

Remove these strings added by the malware/grayware/spyware in the HOSTS file

[ Learn More ]
    • 127.0.0.1 http://vk.com
    • 127.0.0.1 http://m.vk.com
    • 127.0.0.1 http://ok.ru
    • 127.0.0.1 http://playground.ru
    • 127.0.0.1 http://stopgame.ru
    • 127.0.0.1 http://ag.ru
    • 127.0.0.1 http://kaspersky.com
    • 127.0.0.1 http://symantec.com
    • 127.0.0.1 http://free.drweb.com
    • 127.0.0.1 http://drweb.com
    • 127.0.0.1 http://free.drweb.ru
    • 127.0.0.1 http://drweb.ru
    • 127.0.0.1 https://vk.com
    • 127.0.0.1 https://m.vk.com
    • 127.0.0.1 https://ok.ru
    • 127.0.0.1 https://playground.ru
    • 127.0.0.1 https://stopgame.ru
    • 127.0.0.1 https://ag.ru
    • 127.0.0.1 https://kaspersky.com
    • 127.0.0.1 https://symantec.com
    • 127.0.0.1 https://free.drweb.com
    • 127.0.0.1 https://drweb.com
    • 127.0.0.1 http://free.drweb.ru
    • 127.0.0.1 https://drweb.ru
    • 127.0.0.1 vk.com
    • 127.0.0.1 m.vk.com
    • 127.0.0.1 ok.ru
    • 127.0.0.1 playground.ru
    • 127.0.0.1 stopgame.ru
    • 127.0.0.1 ag.ru
    • 127.0.0.1 kaspersky.com
    • 127.0.0.1 symantec.com
    • 127.0.0.1 free.drweb.com
    • 127.0.0.1 drweb.com
    • 127.0.0.1 free.drweb.ru
    • 127.0.0.1 drweb.ru

Step 6

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.
  • %Windows%\tr
  • %Windows%\black.bmp
  • %Windows%\svchost.exe
  • %System Root%\ReadMe.txt

Step 7

Restart in normal mode and scan your computer with your Trend Micro product for files detected as Ransom_ROZALOCK.F117CD. 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 8

Reset your Desktop properties

[ Learn More ]

Step 9

Restore encrypted files from backup.


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