Analysis by: Oliver Ramirez
ALIASES:

Win32/Filecoder.HydraCrypt.M trojan (NOD32); W32.Tapin (NORTON)

 PLATFORM:

Windows

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

  • Threat Type: Ransomware

  • Destructiveness: No

  • Encrypted: No

  • In the wild: Yes

  OVERVIEW

Infection Channel: Downloaded from the Internet

This Ransomware arrives on a system as a file dropped by other malware or as a file downloaded unknowingly by users when visiting malicious sites.

It drops files as ransom note.

  TECHNICAL DETAILS

File Size: 135,168 bytes
File Type: EXE
Memory Resident: No
Initial Samples Received Date: 01 Sep 2017
Payload: Displays message/message boxes, Encrypts files

Arrival Details

This Ransomware 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 Ransomware drops the following copies of itself into the affected system:

  • %ProgramData%\{10 random characters}

(Note: %ProgramData% is the Program Data folder, where it usually is C:\Program Files in Windows 2000, Windows Server 2003, and Windows XP (32- and 64-bit); C:\ProgramData in 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.)

It adds the following processes:

  • cmd.exe /C sc stop VVS
  • cmd.exe /C sc stop wscsvc
  • cmd.exe /C sc stop WinDefend
  • cmd.exe /C sc stop wuauserv
  • cmd.exe /C sc stop BITS
  • cmd.exe /C sc stop ERSvc
  • cmd.exe /C sc stop WerSvc
  • cmd.exe /C vssadmin.exe Delete Shadows /All /Quiet
  • cmd.exe /C bcdedit /set {default} recoveryenabled No
  • cmd.exe /C bcdedit /set {default} bootstatuspolicy ignoreallfailures

Autostart Technique

This Ransomware adds the following registry entries to enable its automatic execution at every system startup:

HKEY_CURRENT_USERS\Software\Microsoft\
Windows\CurrentVersion\Run
{12 random characters} = %ProgramData%\{malware path}

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Run
{10 random characters} = %ProgramData%\{10 random characters}.exe

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\RunOnce
*{10 random characters} = %ProgramData%\{10 random characters}.exe

Other System Modifications

This Ransomware adds the following registry entries:

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion
{10 random characters} = {encryption count}

Ransomware Routine

This Ransomware avoids encrypting files with the following strings in their file name:

  • _HELP_INSTRUCTION.TXT
  • ntldr
  • NTLDR
  • NTDETECT.COM
  • ntdetect.com
  • Desktop
  • DESKTOP

It renames encrypted files using the following names:

  • {32 Random Characters}.arena

It drops the following file(s) as ransom note:

  • {folder of encrypted files}\_HELP_INSTRUCTION.txt

NOTES:
The _HELP_INSTRUCTION.txt contains the following information:

  SOLUTION

Minimum Scan Engine: 9.850
FIRST VSAPI PATTERN FILE: 13.632.02
FIRST VSAPI PATTERN DATE: 01 Sep 2017
VSAPI OPR PATTERN File: 13.633.00
VSAPI OPR PATTERN Date: 02 Sep 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

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\Run
    • {12 random characters} = {malware path}
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Run
    • {10 random characters} = "C:\ProgramData\{10 random characters}.exe"
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\RunOnce
    • {10 random characters} = "C:\ProgramData\{10 random characters}.exe"
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion
    • {10 random characters} = {encryption count}

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.
  • {folder of encrypted files}\\_HELP_INSTRUCTION.txt

Step 5

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