Researchers have yet to discover a killswitch that would prevent the spread of this week's massive ransomware outbreak, but one has found a "vaccine" that can halt the spread of the attack, reports BleepingComputer.
The rapidly spreading ransomware hit businesses, including those in critical infrastructure, across Russia, Ukraine, France, Netherlands, Spain, India, and Denmark. Some experts found similarities with the Petya malware, including its encryption of the Master Boot Record (MBR) on infected systems. Others say this malware hasn't been previously seen and call it NotPetya.
Amit Serper, a security researcher with Cybereason, discovered the ransomware operates by searching for a local file, and will exit the encryption process if the file already existed on the disk. Victims can block the ransomware from executing by creating this file on their machines.
To implement the vaccination, create a file called "perfc" in the "C:\Windows" folder and set it to read-only. Researchers call this a vaccination, not a killswitch, because it only vaccinates the machine where it's stored. A killswitch could be turned on to prevent all incidents of this ransomware.
Read more details here.