Threat Description

Trojan:​Java/Classloader

Details

Aliases: Java.trojan.exploit.bytverify
Category: Malware
Type: Trojan
Platform: Java

Summary



Also known as a trojan horse program, this is a deceptive program that performs additional actions without the user's knowledge or permission. It does not replicate.



Removal



Automatic Disinfection

Allow F-Secure Anti-Virus to disinfect the relevant files.

For more general information on disinfection, please see Removal Instructions.



Technical Details



The Classloader files are Internet Explorer (IE) homepage hijacker trojans that infect IE through malicous web pages, which host exploits targeting the Java classloader byteverify vulnerability in unpatched versions of IE. These trojans usually change the browser start page and search settings and download other trojan/spyware components on the system. These trojans are distributed on malicious web pages that contain references to the trojans. Usually the classloader files are in a .zip or .jar archive along with several other files.

Installation

The Classloader based trojans install themselves from a malicious web page that contains a reference to the trojan. The trojan uses a vulnerability in the classloader system of Microsoft Java runtime, that allows the malicious applet to break out of the sandbox, and gain same access as any other executable running with users permissions.

Payload

After being executed these trojans usually download executable components that are either further parts of the trojan or spyware being dropped by the trojan.

Note

Using the latest version of Internet Explorer and keeping up-to-date with the latest security patches is the easiest way to protect against possible infection from Classloader trojans, as this fixes the web browser vulnerabilities needed for the trojan to work.






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