Analysis by: Alvin Bacani
ALIASES:

Trojan:Win32/Crilock.B (Microsoft); Trojan-Ransom.Win32.Blocker.coew (Kaspersky)

 PLATFORM:

Windows 2000, Windows Server 2003, Windows XP (32-bit, 64-bit), Windows Vista (32-bit, 64-bit), Windows 7 (32-bit, 64-bit)

 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.

  TECHNICAL DETAILS

File Size: 750,080 bytes
File Type: EXE
Memory Resident: Yes
Initial Samples Received Date: 15 Oct 2013

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%\{random filename}.exe

(Note: %Application Data% is the current user's Application Data folder, which is usually C:\Documents and Settings\{user name}\Application Data on Windows 2000, XP, and Server 2003, or C:\Users\{user name}\AppData\Roaming on Windows Vista and 7.)

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
CryptoLocker = ""%Application Data%\{random filename}.exe""

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\RunOnce
*CryptoLocker = ""%Application Data%\{random filename}.exe""

Other Details

This Trojan connects to the following possibly malicious URL:

  • {randomly generated domain}.biz/home
  • {randomly generated domain}.ru/home
  • {randomly generated domain}.net/home
  • {randomly generated domain}.info/home
  • {randomly generated domain}.co.uk/home
  • {randomly generated domain}.com/home
  • {randomly generated domain}.org/home