RANSOM_CRYPTESLA.J

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 modifies the Internet Explorer Zone Settings.

It deletes itself after execution.

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%\{5 random letters}-a.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.)

Other System Modifications

This Trojan adds the following registry keys:

HKEY_CURRENT_USER\Software\zsys

HKEY_CURRENT_USER\Software\{installation ID}

HKEY_CIRRENT_USER\S

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\zsys
ID = {installation ID}

HKEY_CURRENT_USER\S
Acronis = "%Application Data%\{5 random letters}-a.exe"

Web Browser Home Page and Search Page Modification

This Trojan modifies the Internet Explorer Zone Settings.

Dropping Routine

This Trojan drops the following files:

• %User Profile%\Documents\recover_file_{9 random letters}.txt
• %Desktop%\Howto_RESTORE_FILES.txt
• %Desktop%\Howto_RESTORE_FILES.html
• %Desktop%\Howto_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://myexternalip.com/raw

It connects to the following possibly malicious URL:

• https://{BLOCKED}thui5ojcez.tor2web.org/inst.php
• https://{BLOCKED}thui5ojcez.onion.to/inst.php
• http://{BLOCKED}n-1022.net/wp-content/uploads/wysija/misc.php
• http://{BLOCKED}r.ro/wp-content/uploads/wysija/misc.php
• http://{BLOCKED}ecurityafrica.net/wp-content/uploads/wysija/misc.php
• http://{BLOCKED}e-ict.nl/wp-content/uploads/wysija/misc.php
• http://{BLOCKED}smeile.org/wp-content/uploads/wysija/misc.php
• http://{BLOCKED}-banque.org/wp-content/uploads/wysija/misc.php

It opens the following files:

• dropped %Desktop%\Howto_RESTORE_FILES.txt
• dropped %Desktop%\Howto_RESTORE_FILES.html
• dropped %Desktop%\Howto_RESTORE_FILES.bmp

(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 deletes itself after execution.

NOTES:

It appends the extension .vvv to the file name of the encrypted files.

It drops how_recover+{3 random letters}.html and how_recover+{3 random letters}.txt to the folders where the files are encrypted.