Analysis by: Johnlery Triunfante

ALIASES:

Trojan-Ransom.Win32.Locky.a (Kaspersky); Ransom:Win32/Locky.A (Microsoft); W32/Filecoder.BK!tr (Fortinet); Troj/Ransom-CHA (Sophos)

 PLATFORM:

Windows

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

  • Threat Type: Ransomware

  • Destructiveness: No

  • Encrypted:

  • In the wild: Yes

  OVERVIEW

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.

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

  TECHNICAL DETAILS

File Size: 97,792 bytes
File Type: EXE
Memory Resident: Yes
Initial Samples Received Date: 16 Feb 2016

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:

  • %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 Ransomware creates the following registry entries to enable automatic execution of dropped component at every system startup:

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Run
Locky = "%User Temp%\svchost.exe"

Other System Modifications

This Ransomware adds the following registry keys:

HKCU\Software\Locky

Other Details

This Ransomware connects to the following possibly malicious URL:

  • http://{BLOCKED}.{BLOCKED}.181.169
  • http://{BLOCKED}.{BLOCKED}.33.206
  • {Domain Generated Algorithm}.{ru, be, yt, us}

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

It is capable of encrypting files in the affected system.

  SOLUTION

Minimum Scan Engine: 9.850
FIRST VSAPI PATTERN FILE: 12.830.05
FIRST VSAPI PATTERN DATE: 11 Oct 2016
VSAPI OPR PATTERN File: 12.831.00
VSAPI OPR PATTERN Date: 12 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

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
    • Locky

Step 5

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"

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.
  • %User Temp%\svchost.exe

Step 7

Restart in normal mode and scan your computer with your Trend Micro product for files detected as Ransom_LOCKY.SM3. 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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