TROJ_CRYPCTB.MGH

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.

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:

• %Windows%\Tasks\{Random Filename 2}.job
• %All Users Profile%\Application Data\Sun\{Random Filename 3}
• %All Users Profile%\Application Data\{Random Filename 4}.html
• %User Profile%\My Documents\Decrypt All Files {7 Random Letters}.txt
• %User Profile%\My Documents\Decrypt All Files {7 Random Letters}.bmp

(Note: %Windows% is the Windows folder, where it usually is C:\Windows on all Windows operating system versions.. %All Users Profile% is the All Users folder, where it usually is C:\Documents and Settings\All Users on Windows 2000, Windows Server 2003, and Windows XP (32- and 64-bit); C:\ProgramData 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.. %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.)

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

• %User Temp%\{Random Filename 1}.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.)

Other System Modifications

This Trojan adds the following registry keys:

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
ESENT\Process
{Random Letters} =

It modifies the following registry entries:

HKEY_CURRENT_USER\Control Panel\Desktop
Wallpaper = "%User Profile%\My Documents\Decrypt All Files {7 Random Letters}.bmp

(Note: The default value data of the said registry entry is "{User Preference}".)

HKEY_CURRENT_USER\Control Panel\Desktop
WallpaperStyle = "0"

(Note: The default value data of the said registry entry is {User Preference}.)

Other Details

This Trojan connects to the following possibly malicious URL:

• http://ip.{BLOCKED}e.com/
• http://tzsvejrzduo52siy.{BLOCKED}n.gq
• http://tzsvejrzduo52siy.{BLOCKED}n.lt
• http://tzsvejrzduo52siy.{BLOCKED}n.gq
• http://tzsvejrzduo52siy.{BLOCKED}n.lt

NOTES:

This Trojan drops the following files in various folders:

• Decrypt All Files {7 Random Letters}.txt
• Decrypt All Files {7 Random Letters}.bmp

It encrypts files with certain extensions then appends .{7 random characters} as the new file extension of the encrypted files.

The registry modifications are for changing the affected system's wallpaper. The new wallpaper informs the user that his files are encrypted and displays the instructions on how to decrypt the files.