Fivesys rootkit exploits Microsoft certification system

- Posted in Exploit by

Fivesys is a rootkit that has been recently discovered in the wild. A rootkit is a type of malware designed to install in the background on a target machine and are also designed to be hard to impossible to detect by normal malware scanning and remediation processes. Rootkits as a class of malware isn't new, but the viability of rootkits overall, has been reduced due to countermeasures developed to mitigate the vast majority of rootkits on the internet. The difference with this rootkit is its packaging that mimics a valid signed driver; it even has a Microsoft signed certificate.

The purpose of the Fivesys rootkit to date, is to redirect HTTP/HTTPS traffic to an attackers predefined IP addresses. The current package has a list of 300 different IPs through proxy designed to prevent blocking traffic. The package also contains a driver blacklist to prevent it being removed or overwritten with a legitimate package. It is it thought by Bitdefender, the company that made the discovery, that the primary target of Fivesys is online games, with the intent to steal game login credentials and hijack in-game transactions for payment credentials/data. As the prior statement cannot be fully verified at this time, we would like to note that re-programming of the package will likely occur resulting in Fivesys being weaponized for any number of similar attack vectors.

As I outline in my first paragraph, the major issue with Fivesys is that the creator has managed to pass the package through Microsoft's driver validation program, which we have confirmed is a fully automated signing process with no manual oversight or flag for review. This allows an actor to use the process to bypasses all of the inbuilt windows security features, leaving machines vulnerable until it is discovered.


Our recommendation to prevent Fivesys or any other rootkits from affecting your environment is to be diligent in your downloads by confirming you are on the manufacturers site. Input the url to the manufacturer manually, do not click on links, and do not use the google search to click a link to go to the download. Current exploits in AdSense and other links, advertising links to legitimate sites that are user uploaded sources, all pose a real risk to Fivesys being downloaded instead of the legitimate driver/software you are after - see our posts on the AdSense exploit. Make sure all your teams, staff and users are trained on cyber security.