RANSOM_LOCKY.KCN

April 19, 2016
 Modified by: Janus Agcaoili
 ALIASES:

Ransom:Win32/Locky.A (Microsoft), Ransom.Locky (Malwarebytes)

 PLATFORM:

Windows

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

  • Threat Type: Trojan

  • Destructiveness: No

  • Encrypted: Yes

  • 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.

However, as of this writing, the said sites are inaccessible. It is capable of encrypting files in the affected system.

  TECHNICAL DETAILS

File Size:

204,800 bytes

File Type:

EXE

Memory Resident:

No

Initial Samples Received Date:

23 Mar 2016

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 files:

  • %Desktop%\_HELP_instructions.txt - ransom note
  • %Desktop%\_HELP_instructions.bmp - image used as wallpaper
  • {folders containing encrypted files}\_HELP_instructions.txt - ransom note

(Note: %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.)

It drops the following copies of itself into the affected system:

  • %User Temp%\svchost.exe

(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.)

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
Locky = "%User Temp%\svchost.exe"

Other System Modifications

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

HKEY_CURRENT_USER\Control Panel\Desktop
Wallpaper = "%Desktop%\_HELP_instructions.bmp"

It adds the following registry keys as part of its installation routine:

HKEY_CURRENT_USER\Software\{random characters}

Other Details

This Trojan connects to the following possibly malicious URL:

  • http://{BLOCKED}.{BLOCKED}.154.126/main.php
  • http://{BLOCKED}.{BLOCKED}.170.244/main.php
  • http://{BLOCKED}.{BLOCKED}.87.106/main.php
  • {Random Generated URL}

It renames encrypted files using the following names:

  • {random string}.locky

However, as of this writing, the said sites are inaccessible.

It is capable of encrypting files in the affected system.

  SOLUTION

Minimum Scan Engine:

9.800

FIRST VSAPI PATTERN FILE:

12.422.02

FIRST VSAPI PATTERN DATE:

24 Mar 2016

VSAPI OPR PATTERN File:

12.423.00

VSAPI OPR PATTERN Date:

25 Mar 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

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
    • Locky = "%User Temp%\svchost.exe"
  • In HKEY_CURRENT_USER\Control Panel\Desktop
    • Wallpaper = "%Desktop%\_HELP_instructions.bmp"

Step 5

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.
  • %Desktop%\_HELP_instructions.bmp
  • %Desktop%\_HELP_instructions.txt
  • {folders containing encrypted files}\_HELP_instructions.txt

Step 6

Restart in normal mode and scan your computer with your Trend Micro product for files detected as RANSOM_LOCKY.KCN. 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 7

The following created files/folders/registry keys/registry entries cannot be identified by the user since there are no reference values in the created key. The only way it can be identified is by comparing the present system information with a backup. Note that the said components do not have to be deleted since it won't be harmful to the system.

  • HKEY_CURRENT_USER\Software\{random characters}

Step 8

Restore encrypted files from backup.


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