RANSOM_CRYPTESLA.CBQ163B

April 04, 2016
 Analysis by: Jeanne Jocson
 ALIASES:

Ransom:Win32/Tescrypt.A(Microsoft), Win32/Kryptik.EQVX(ESET)

 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:

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 the initially executed copy of itself.

  TECHNICAL DETAILS

File Size:

471,040 bytes

File Type:

EXE

Initial Samples Received Date:

11 Mar 2016

Payload:

Connects to URLs/IPs, Displays message, Encrypts files, Drops files

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 a copy of itself in the following folders using different file names:

  • %Windows%\{random file name}.exe

(Note: %Windows% is the Windows folder, where it usually is C:\Windows on all Windows operating system versions.)

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
{random} = "%System%\cmd.exe /c start "" "%Windows%\{random filename}.exe""

Other System Modifications

This Trojan adds the following registry keys:

HKEY_CURRENT_USER\Software\zzzsys

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\zzzsys
ID = {Installation ID}

Dropping Routine

This Trojan drops the following files:

  • %User Profile%\Documents\recover_file_{random letters}.txt
  • %Desktop%\_ReCoVeRy_.TXT
  • %Desktop%\_ReCoVeRy_.HTM
  • %Desktop%\_ReCoVeRy_.png
  • {folders containing encrypted files}\_ReCoVeRy_+{random letters}.png
  • {folders containing encrypted files}\_ReCoVeRy_+{random letters}.txt
  • {folders containing encrypted files}\_ReCoVeRy_+{random letters}.html

(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 possibly malicious URL:

  • http://{BLOCKED}hop.net/wcspng.php
  • http://{BLOCKED}raining.com/wp-includes/theme-compat/wcspng.php
  • http://{BLOCKED}gfeng.cn/images/lurd/wcspng.php
  • http://{BLOCKED}freaknetworks.com/dev/wp-content/uploads/2015/07/wcspng.php
  • http://{BLOCKED}randphone.com/wp-content/themes/storefront/wcspng.php
  • http://{BLOCKED}annel.com/wp-admin/maint/wcspng.php

It deletes the initially executed copy of itself