If the worst happens, the nasty virus has invaded your system, then you still have options. Backup important files because you may be locked out of your desktop by Ransomware, a nasty piece of Malware that completely locks up your machine. Never give the unscrupulous creator of this hijacking invader satisfaction. Do not make a payment! Have the backups on hand and reset the computer by reinstalling your operating system before ever taking that route. If you don't have a backup plan, take a look at this link, Microsoft's own view of Ransomware.
Malware disguises itself as a legitimate service in order to evade virus scans. Meanwhile, a sly virus gives the programmer a foothold you simply can't afford. Private data is exposed, including passwords and financial information. Disconnect your computer from the internet. Run a scan and remove the infections. It seems like the detection algorithm missed the attack, so replace it with another one. There's no shortage of options as proven by the choices above. Also, reinforce the antivirus solution with a good firewall and a malware application.
Virus attacks come in two forms. There's the hidden chameleon-like trooper, the assailant that secretly scans your computer for sensitive data. The second type is the troublemaker. The chaotic variant starts random ads, opens weird radio stations, and makes dramatic changes to everything. Weird search bars are added to your browser. Numerous pop ups make life difficult, and every web page you navigate seems to involve at least one frustrating redirect. Again, make backups of critical files. Try a system restore, but know that you may never fully trust your operating system again. To ease your concerns at this point, carry out continual scans to monitor the system for new infections, and, as a last resort, conduct a full reinstallation of the operating system. Windows 10 now makes this latter move easier than ever before by offering a full reset without losing your files (see Recovery Options for more information).
We've probably made Microsoft Windows and other operating systems sound like a minefield of potential infections, but many users experience years of happy computing without ever running into a virus. Just stay away from suspect websites, don't click on or downloads random links, and always, always take the precautionary measure of having one of these antivirus packages installed and running.