Threat description


Category: Malware
Type: Trojan-Spy
Platform: W32


This type of trojan secretly installs spy programs and/or keylogger programs.


Automatic action

Depending on the settings of your F-Secure security product, it will either automatically delete, quarantine or rename the suspect file, or ask you for a desired action.

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You may also refer to the Knowledge Base on the F-Secure Community site for more information.

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Technical Details

Trojan-Spy:W32/Banker.JAG is delivered to a machine by a dropper program. Once installed and executed, the trojan-spy logs all keystrokes entered into a web form; the stolen information can then be retrieved by the attacker.Banker.JAG primarily targets banking websites and includes a functionality to inject a script into specified webpages. The injected script requests account details from the user; as it is injected into a legitimate banking site webpage, an unsuspecting user may be deceived into giving away their confidential information.The malware also includes functionality to perform various actions (mostly malicious) on the infected machine.


The Banker dropper program drops a DLL component, together with its configuration file, to the %System% folder. It then enables the use of browser extensions and injects the DLL component as a browser helper object (BHO) into the browser process.The DLL component is detected as Trojan-Downloader.Win32.BHO.kif and is capable of creating a LOG file to contain:

  • Stored Passwords for password-protected sites and MSN Login
  • Cookies
  • Certificates
  • Content of HOSTS file

While active, the trojan-spy logs all keyboard input used to fill in online forms via the web browser. To enhance its data-stealing activity, the trojan-spy disables the browser's AutoComplete Field setting. If turned on, the AutoComplete automatically fills in fields in web forms without the user needing to type in any further details; the trojan-spy is therefore unable to capture all the information. Disabling the AutoComplete function forces the user to manually type in the details again and allows the trojan-spy to capture all the information.In addition to its main data-stealing functionality, the trojan-spy is also capable of a number of malicious actions affecting the computer system itself. It is capable of carrying out the following commands:

  • Reloading the configuration to memory
  • Executing files on the system
  • Retrieving stolen information / get system information
  • Deleting itself
  • Deleting cookies
  • Grabbing cookies
  • Downloading files
  • Uploading Bank of America Keys
  • Removing Bank of America keys
  • Logging contents of Protected Storage
  • Copying user Certificates
  • Corrupting Windows by deleting NTLDR and NTDETECT.COM
  • Corrupting Windows by deleting NTLDR and NTDETECT.COM THEN REBOOT
  • Rebooting the system
  • Removing the cache of grabbed Items in order to grab some more
  • Adding or removing data redirection in the hosts file

Directions for performing these actions may be transmitted when the malware connects to its command and control server (C&C) to receive any further commands from the attacker:


The trojan-spy also checks the browser's URL access to see if any of the following keywords are present:

  • akbank

If any of these keywords are present, the trojan-spy injects a script into the page to ask for additional information. A sample of the injected script is as follows:

url="citibank"  before="name=password>"  what="   

To prevent fraud enter your credit card information please: Your ATM or Check Card Number: Expiration Date: (e.g. 07.2007) ATM PIN: Your mother's maiden name:

" block="sign-on."  check="pin" quan="4" content="d" >   

Description Created: 2009-04-01 05:20:14.0

Description Last Modified: 2009-04-01 05:55:59.0


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