Gribble
Summary
Gribble is a trojan that has been available an a web page that uses a Java Virtual Machine vulnerability in Internet Explorer to drop and execute the worm.
Further infromation about the vulnerability, including a fix, is available from Microsoft: https://www.microsoft.com/technet/security/bulletin/MS00-075.asp
Removal
Based on the settings of your F-Secure security product, it will either move the file to the quarantine where it cannot spread or cause harm, or remove it.
A False Positive is when a file is incorrectly detected as harmful, usually because its code or behavior resembles known harmful programs. A False Positive will usually be fixed in a subsequent database update without any action needed on your part. If you wish, you may also:
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Check for the latest database updates
First check if your F-Secure security program is using the latest updates, then try scanning the file again.
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Submit a sample
After checking, if you still believe the file is incorrectly detected, you can submit a sample of it for re-analysis.
Note: If the file was moved to quarantine, you need to collect the file from quarantine before you can submit it.
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Exclude a file from further scanning
If you are certain that the file is safe and want to continue using it, you can exclude it from further scanning by the F-Secure security product.
Note: You need administrative rights to change the settings.
Technical Details
When the trojan is executed, it creates "jb.vbs" file into the root of the current drive. This file is executed.
Afther that the trojan drops another VBS file, "C:\lipreffs.vbs". This file is executed as well when it adds itself to to the registry in a such way that it is executed when the system is restarted. It also starts to send large ICMP echo (ping) packets to the gnc.com.
Next Gribble goes trough all drives, and if it is able to locate a mIRC installation, it will create "script.ini" and modify the "mirc.ini" so, that it will be loaded when the IRC client is started.
Finally the trojan deletes "c:\jb.vbs".
The modified "script.ini" will attempt a Denial of Service attack agains grc.com when a connection is made with the mIRC client. DoS attack consists of random HTTP requests to either www.grc.com or grc.com, and garbage sent to the grc.com DNS server.
Further the trojan sends offensive messages when another user joins a channel where the infected user is.
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