BleepingComputer.com: Java was infected with a trojan?

PLEASE NOTE: I am not looking for help with removal or any such thing. I am looking for insight and answers into this occurrence.

I just did my first scan with MSE today and it came up with 2 threats which no other anti-malware program I have used had ever detected. (NOD32, AVG, MBAM) I am using Windows 7 64-Bit. They were as follows:

* Trojan.Downloader:Java/OpenConnection.EM
* "Items:
containerfile:C:\Users\PC\AppData\LocalLow\Sun\Java\Deployment\cache\6.0\29\445d6bdd-432d96eb
containerfile:C:\Users\PC\AppData\LocalLow\Sun\Java\Deployment\cache\6.0\52\577b1c34-63e44de0
file:C:\Users\PC\AppData\LocalLow\Sun\Java\Deployment\cache\6.0\29\445d6bdd-432d96eb->yahoo/InfoCtrl.class
file:C:\Users\PC\AppData\LocalLow\Sun\Java\Deployment\cache\6.0\52\577b1c34-63e44de0->yahoo/InfoCtrl.class


* Trojan:Java/Mugademel.A
* Items:
containerfile:C:\Users\PC\AppData\LocalLow\Sun\Java\Deployment\cache\6.0\11\2c9ba28b-586cb43d
containerfile:C:\Users\PC\AppData\LocalLow\Sun\Java\Deployment\cache\6.0\4\53100c4-44518453
file:C:\Users\PC\AppData\LocalLow\Sun\Java\Deployment\cache\6.0\11\2c9ba28b-586cb43d->JavaUpdateManager.class
file:C:\Users\PC\AppData\LocalLow\Sun\Java\Deployment\cache\6.0\4\53100c4-44518453->JavaUpdateManager.class


This concerns me because to date I've scanned with programs such as NOD32, AVG, MBAM, SB S&D among many others and NONE have picked up any type of infection relating to this Java issue. Is this a false positive? Why is this occuring and what are the implications of it?



Your help is greatly appreciated.

Thanks

This post has been edited by fgeelo: 16 August 2010 - 12:32 AM

Your questions are already being addressed here by JimR1, Microsoft MVP Consumer Security - Forum Moderator - Live One Care - Live Mesh - Microsoft Security Essentials. Since your questions specifically involve MSE, those experts using MSE are probably in the best position to answer them.

FYI: When a browser runs an applet, the Java Runtime Environment (JRE) stores the downloaded files into its cache folder (C:\Documents and Settings\username\Application Data\Sun\Java\Deployment\cache) for quick execution later and better performance. Both good and malicious applets are stored in the Java cache directory and your anti-virus may detect them and provide alerts. Notification of these files as a threat does not always mean that a machine has been infected; it indicates that a program included the viral class file but this does not mean that it used the malicious functionality. However, when alerted to this type of threat, it's a good practice to clear the Java cache and clean out Windows temporary files.

For more specific information about Java exploits, please refer to Virus found in the Java cache directory. Also be aware that older versions of Java have vulnerabilities that malicious sites can use to exploit and infect your system. That's why it is important to always use the most current Java Version and remove outdated Java components.