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Trojan:Win32/Ransirac.G

First posted on 17 March 2012.
Source: Microsoft

Aliases :

There are no other names known for Trojan:Win32/Ransirac.G.

Explanation :

Trojan:Win32/Ransirac.G is a trojan that locks the affected user's computer, and attempts to scare and intimidate the user into paying money to regain access to their infected computer.


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Trojan:Win32/Ransirac.G is a trojan that locks the affected user's computer, and attempts to scare and intimidate the user into paying money to regain access to their infected computer.



Installation

When executed the malware copies itself as "gema.exe" to the following locations:

• <system folder>
• c:\documents and settings\all users\application data\gema
• c:\documents and settings\administrator\application data\gema

Note: <system folder> refers to a variable location that is determined by the malware by querying the operating system. The default installation location for the system folder for Windows 2000 and NT is C:\Winnt\System32; and for XP, Vista, and 7 is C:\Windows\System32.

It modifies the following registry entries to ensure its execution at each Windows start:

In subkey: HKLM\software\Microsoft\Windows\CurrentVersion\Run
Sets value: "gema"
With data: "<system folder>\gema.exe"

In subkey: HKLM\SOFTWARE\Microsoft\Windows NT\CurrentVersion\winlogon
Sets value: "userinit"
With data: "<system folder>\gema.exe,<system folder>\userinit.exe,"

In subkey: HKCU\software\Microsoft\Windows\CurrentVersion\Run
Sets value: "gema"
With data: "<AppData>\gema\gema.exe"

In subkey: HKCU\software\Microsoft\Windows NT\CurrentVersion\Winlogon
Sets value: "shell"
With data: "<AppData>\gema\gema.exe,explorer.exe"



Payload

Displays messages

Once infected, Trojan:Win32/Ransirac.G displays a message which is designed to trick the user into paying money to 'unlock' the computer, so they can regain access.

It contacts the following domains to download HTML, which is then displayed by the trojan:

• elektropedi.com
• fazlaoluyoruz.com
• gunestekstilemlak.com
• keremcatak.com.tr

Below is an example of a message it displays when it locks the computer, where the affected user is accused of illegally downloading music files:



It should be noted that in order to appear legitimate, the HTML uses style sheet information and images from the real organization's website GEMA, which it attempts to mimic.

Terminates processes

The trojan checks for, and terminates the following process if found running on the affected computer:

• procexp.exe
• taskmgr.exe

Additional information

The trojan may also write the following file:

"win.ini"

under directory

%windir%



Analysis by Ray Roberts

Last update 17 March 2012

 

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