Ransom Away can scan for the read-only perfc.dat file that the Petya ransomware attacks, notify you if it exists and adds it if it doesn't.

Ransom Away is portable, and it will create a perfc.dat file in the Windows\System32 directory if needed. It is known that the Petya ransomware does not run if this file is found. Unless someone makes a new strain that works around it, but that for another day.

It only takes seconds to run and shows a log file if perfc.dat was created. If perfc.dat already exists, then you're told that your PC is already immune. We opened the file it created, and all it did was create a file with @ for the content.

You could just as easily do the same thing with Notepad and enter anything you like and save it as a read-only perfc.dat in your Windows\System32 folder. Considering how many tools have now been created to do just that, we think that might be a better bet.

That said, Ransom Away is free, portable and fast so if you're not into doing it the manual way, here's another solution to protect your computer from the Petya ransomware.