Updated 3:19PM Pacific Time: A method to ‘vaccinate’ yourself against this ransomware variant has been found. I have posted details towards the end of the post along with a batch file you can run. It is as simple as creating the file C:\Windows\perfc and marking it read-only. Update 2 at 7pm PST on Tuesday: It appears that … Continue reading PSA: Petya Ransomware Affecting Critical Systems Globally: Here’s What to Do.