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RANSOM_CRYPTESLA.NMQ

February 10, 2016
 ALIASES:

Ransom:Win32/Tescrypt.A (Microsoft), Win32/Filecoder.TeslaCrypt.D (ESET-NOD32), Trojan.Cryptolocker.N (Symantec)

 PLATFORM:

Windows

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

  • Threat Type: Trojan

  • Destructiveness: No

  • Encrypted:

  • 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 deletes itself after execution. It is capable of encrypting files in the affected system.

  TECHNICAL DETAILS

File Size:

355,548 bytes

File Type:

EXE

Memory Resident:

Yes

Initial Samples Received Date:

04 Sep 2015

Payload:

Encrypts files, Connects to URLs/IPs

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:

  • %Application Data%\vc{4 random letters}.exe

(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.)

Autostart Technique

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

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Run
vssadm = "%Application Data%\vc{4 random letters}.exe"

Other System Modifications

This Trojan adds the following registry keys:

HKEY_CURRENT_USER\Software\msys

HKEY_CURRENT_USER\Software\{installation ID}

It adds the following registry entries:

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\Policies\
System
EnabledLinkConnections = "1"

HKEY_CURRENT_USER\Software\{installation ID}
data = "{encryption information}"

HKEY_CURRENT_USER\Software\msys
ID = "{installation ID}"

Dropping Routine

This Trojan drops the following files:

  • %User Profile%\Documents\Recovery_File_{random letters}.txt
  • %Desktop%\RESTORE_FILES.TXT
  • %Desktop%\RESTORE_FILES.HTML
  • %Desktop%\RESTORE_FILES.BMP

(Note: %User Profile% is the current user's profile folder, which is usually C:\Documents and Settings\{user name} on Windows 2000, XP, and Server 2003, or C:\Users\{user name} on Windows Vista and 7.. %Desktop% is the desktop folder, where it usually is C:\Documents and Settings\{user name}\Desktop in Windows 2000, Windows Server 2003, and Windows XP (32- and 64-bit); C:\Users\{user name}\Desktop 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.)

Other Details

This Trojan connects to the following URL(s) to get the affected system's IP address:

  • http://ipinfo.io/ip

It connects to the following possibly malicious URL:

  • http://www.{BLOCKED}iso.cl/wp-content/themes/r.php?{Value}
  • http://{BLOCKED}ppen.nl/wp-content/themes/r.php?{Value}
  • http://{BLOCKED}erheath.ru/wp-content/themes/r.php?{Value}
  • http://{BLOCKED}erests.com/wp-content/themes/r.php?{Value}
  • http://{BLOCKED}erests.com/wp-content/themes/r.php?{Value}
  • http://{BLOCKED}tynowbooksandgifts.com/wp-content/themes/r.php?{Value}

It renames encrypted files using the following names:

  • {Original file name}.{Original Extension}.abc

It does the following:

  • It drops restore_files_{random letters}.html and restore_files_{random letters}.txt to the folders where the files are encrypted

It deletes itself after execution.

It is capable of encrypting files in the affected system.

  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

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\Run
    • vssadm = "%Application Data%\vc{4 random letters}.exe"
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Policies\System
    • EnabledLinkConnections = "1"

Step 5

Delete this registry key

[ 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
    • msys
  • In HKEY_CURRENT_USER\Software
    • {installation ID}

Step 6

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.
  • Recovery_File_{random letters}.txt
  • RESTORE_FILES.TXT
  • RESTORE_FILES.HTML
  • RESTORE_FILES.BMP
  • restore_files_{random letters}.html
  • restore_files_{random letters}.txt

Step 7

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

Restore encrypted files from backup.


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