In the wild, we have observed that the malicious java class is bundled with non-malicious Java class applets in a JAR file, as in the following examples:
This vulnerability allows remote attackers to execute arbitrary code on vulnerable installations of Sun Java Runtime. Authentication is not required to exploit this vulnerability.
The specific flaw exists within the code responsible for ensuring proper privileged execution of methods. If an untrusted method in an applet attempts to call a method that requires privileges, Java will walk the call stack and for each entry verify that the method called is defined within a class that has that privilege. However, this does not take into account an untrusted object that has extended the trusted class without overwriting the target method. Additionally, this can be bypassed by abusing a similar trust issue with interfaces. An attacker can leverage these insecurities to execute vulnerable code under the context of the user invoking the JRE.
When loaded, it checks if the system is running Windows Operating system thenproceeds with its installation process.
When the user visits a website that contains the applet, which attempts to retrieve a URL parameter from the HTML code that loaded it, or from another Java class. It then attempts to download and execute a file from the retrieved URL
After successful exploitation, it downloads malicious file to the local system and execute it as
- %UserProfile%\ <RANDOM number>.exe
Also, it sets the value of "java.net.useSystemProxies" parameter to "true".