RANSOM_CERBER.BC

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 uses the Windows Task Scheduler to add a scheduled task that executes the copies it drops.

It modifies the Internet Explorer Zone Settings.

It deletes the initially executed copy of itself. It is capable of encrypting files in the affected system.

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%\{GUID}\{random file from system32 folder}.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.)

It drops the following component file(s):

• %Desktop%\# DECRYPT MY FILES #.txt
• %Desktop%\# DECRYPT MY FILES #.html
• %Desktop%\# DECRYPT MY FILES #.vbs
• {folders containing encrypted files}\# DECRYPT MY FILES #.txt
• {folders containing encrypted files}\# DECRYPT MY FILES #.html
• {folders containing encrypted files}\# DECRYPT MY FILES #.vbs
• %Tasks%\{random filename from system32 folder}

(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 uses the Windows Task Scheduler to add a scheduled task that executes the copies it drops.

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 filename from system32 folder} = "%Application Data%\{GUID}\{random filename from system32 folder}.exe"

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\RunOnce
{random filename from system32 folder} = "%Application Data%\{GUID}\{random filename from system32 folder}.exe"

HKEY_CURRENT_USER\Software\Microsoft\
Command Processor
AutoRun = "%Application Data%\{GUID}\{random filename from system32 folder}.exe"

(Note:This registry entry runs the malware each time start Command Processor (Cmd.exe) is executed)

HKEY_CURRENT_USER\Control Panel\Desktop
SCRNSAVE.EXE = "%Application Data%\{GUID}\{random filename from system32 folder}.exe"

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Policies\
Explorer
Run = "%Application Data%\{GUID}\{random filename from system32 folder}.exe"

It drops the following file(s) in the Windows User Startup folder to enable its automatic execution at every system startup:

• %User Startup%\{random filename from system32 folder}.lnk

(Note: %User Startup% is the current user's Startup folder, which is usually C:\Documents and Settings\{user}\Start Menu\Programs\Startup on Windows 2000 and XP, and C:\Documents and Settings\{User name}\Start Menu\Programs\Startup on Windows Vista, 7, and 8.)

Other System Modifications

This Trojan modifies the following file(s):

• It renames encrypted files to {random name}.cerber

It modifies the following registry key(s)/entry(ies) as part of its installation routine:

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Internet Settings
ProxyServer = "http=127.0.0.1:8888;https=127.0.0.1:8888;"

(Note: The default value data of the said registry entry is {user-defined}.)

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Internet Settings
ProxyEnable = "1"

(Note: The default value data of the said registry entry is {user-defined}.)

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Internet Settings
ProxyOverride = "<-loopback>;"

(Note: The default value data of the said registry entry is {user-defined}.)

It also creates the following registry entry(ies) as part of its installation routine:

HKEY_CURRENT_USER\Printers\Defaults\
{GUID}
Component_01 = "{base64 of encoded key}"

HKEY_CURRENT_USER\Printers\Defaults\
{GUID}
Component_00 = "{encoded value}"

Web Browser Home Page and Search Page Modification

This Trojan modifies the Internet Explorer Zone Settings.

Other Details

This Trojan connects to the following possibly malicious URL:

• {BLOCKED}.{BLOCKED}.0/63.0/255
• http://ipinfo.io/json
• http://freegeoip.net/json
• http://ip-api.com/json

It deletes the initially executed copy of itself

It is capable of encrypting files in the affected system.