JS_NELOWEG.DD

This malware is a backdoor with the primary purpose of stealing information from online transactions. The list of the monitored URLs can also be dynamically updated by a cybercriminal. It also has features to enable it to run on Windows Vista and Windows 7.

To get a one-glance comprehensive view of the behavior of this Backdoor, refer to the Threat Diagram shown below.

This backdoor may be dropped by other malware.

It executes commands from a remote malicious user, effectively compromising the affected system.

Arrival Details

This backdoor may be dropped by the following malware:

• BKDR_NELOWEG.DD

Backdoor Routine

This backdoor executes the following commands from a remote malicious user:

• !storage! – retrieves the stored passwords of the browser where this malware is running, and sends it to the C&C server
• !block! – set the registry entry HKEY_CURRENT_USER\UDP !block!
• !screen! – set the registry entry HKEY_CURRENT_USER\UDP !screen!
• !filter! – set the registry entry HKEY_CURRENT_USER\UDP !filter!
• !alt! – set the registry entry HKEY_CURRENT_USER\UDP !alt! which would contain the alternate C&C servers
• !tickit! – set the registry entry HKEY_CURRENT_USER\UDP !tickit!
• !content! – create the registry key HKEY_CURRENT_USER\UDP\c and set registry entries in it
• !reder! – create the registry key HKEY_CURRENT_USER\UDP\r and set registry entries in it
• !cmd! – download a file and execute it
• !kill! – delete the files C:\boot.ini, %System%\dllcache\userinit.exe and %System%\userinit.exe, and forcefully restarts the PC

(Note: %System% is the Windows system folder, which is usually C:\Windows\System on Windows 98 and ME, C:\WINNT\System32 on Windows NT and 2000, or C:\Windows\System32 on Windows XP and Server 2003.)

NOTES:

It gets the C&C server from the following registry entries:

HKEY_CURRENT_USER\UDP
g = "{obfuscated C&C server URL}"

HKEY_CURRENT_USER\UDP
!alt! = "{obfuscated alternate C&C server URLs}"

When the browser loads a web page, it checks if the URL is defined in HKEY_CURRENT_USER\UDP\c. If the URL is defined, it injects HTML with JavaScript codes to the loading web page.

It checks if the URL is defined in the following registry entry:

HKEY_CURRENT_USER\UDP
!block! = "{list of URLs to block}"

If it is found in !block!, the URL is blocked and redirected to another URL defined in the following registry entry:

HKEY_CURRENT_USER\UDP
!reder! = "{list of URLs to redirect to}"

It hooks to submit, click, and keypress events. When a form is submitted, it sends the target URL with all the form data to the C&C server. When a button or link is clicked, the target URL is sent to the C&C server. When a keypress event is detected and the pressed key is Entering, the target URL together forms data (if the Enter key is used to submit a form) and is sent to the C&C server.

This JavaScript runs under Mozilla Firefox.