For those who do not know, when "ordinary" malware sends a sudden "pop-up" to your screen that you did not expect DO NOT TOUCH ANY KEY! Not even the "close X!! NOTHING! NOT EVEN A SHUT DOWN! NOT even the "power" button on the computer! Just leap for the power plug and cut the power! Best if you use a close-by power strip with a button kill. At the pop-up stage the malware is only in the short-term memory, and killing the power deletes all temporary files in the short-term memory. Even trying to shut off the computer without first cutting the power invites the malware in and it takes over in an instant.
IF you catch something that is NOT bomb-proof like Ransomware, you can run an anti-malware program to cleanse it BUT ONLY WITH THE INTERNET CONNECTION PHYSICALLY REMOVED FIRST! If the cable or modem is still connected to your computer, most malware can RELOAD THEMSELVES FASTER THAN YOU CAN DELETE THEM! You gotta first cut the power, then physically remove the internet connection from the computer , then power up and run your best anti-virus, anti-malware program WITHOUT CONNECTION TO THE INTERNET. Then connect to the internet BUT ONLY TO YOUR SECURITY PROGRAM FOR AN UPDATE. Then cut the cable to computer connection again and run the security program AGAIN! BELIEVE ME. It really might work—I have done it. But, I do NOT know if this will work for Ransomware, and probably not if you are on a network. IT IS WORTH A TRY.