Threat Description



Aliases: Needy.F, Java/Needy.F
Category: Malware
Platform: W32


Needy.F is a Java applet based trojan that changes the Internet Explorer start page changes search settings to ones contained in the trojan and downloads a trojan downloader. Needy activates when user views a web page or HTML E-mail that contains reference to the trojan file.


Automatic action

Once detected, the F-Secure security product will automatically disinfect the suspect file by either deleting it or renaming it.


Detailed instructions for F-Secure security products are available in the documentation found in the Downloads section of our Home - Global site.

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

Technical Details

The Needy.F is activated when a web site containing the trojan is loaded with unpacthed Microsoft Internet Explorer browser. When the JAR file containing the trojan is executed it uses Microsoft Internet Explorer VerifierBug vulnerability to get full privileges by escaping the Java security, and execute its code.

When executed the trojan downloads a list of instructions from a web site, by which the trojan trojan modifies the Internet Explorer start page to point to the site where the trojan is downloaded from, changes search settings and adds addresses to the visited pages history.

Unlike earlier variants on Needy family Needy.F is directed by instructions downloaded from a web page. The web page can specify what to which page the trojan changes the Internet start page and search settings. Also the page contains a list of web sites that are copied into the Internet Explorer page history, to make it appear that user would have been visiting certain pornographic services.

In addition to changing the Internet Explorer settings the trojan tries to download a trojan from a website and execute it. Although this page seems no longer to contain the trojan executable.


Detection in F-Secure Anti-Virus was published on April 2nd, 2004 in update:

Detection Type: PC
Database: 2004-04-02_01

Description Details: Jarno Niemela, April 2nd, 2004;


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