Signs that your computer is possibly infested with a computer virus

Computer viruses and other kinds of malware can cause serious problems for your computer. Some malware replicates itself until it fills up all available space on your hard drive, some corrupt data on your computer. Some malware will gain remote access to your computer.
You can avoid most malware by:
Installing reliable anti-virus software; If your anti-virus software is up to date, you should have nothing much to worry about.
staying away from a few common traps.
But once in a while, computer viruses get beyond our defenses. Maybe our anti-virus software is out of date or has been compromised
Common signs to watch out for
There are several signs that could indicate the presence of malware on your computer. Though none of these guarantee the presence of a virus, they do suggest that something is wrong with your computer system.
If your anti-virus software is strong and up to date, you may receive an alert during a scanning process on your computer.
if your software is outdated or the virus is stron enough to deactivate the anti-virus program, you may not be alerted to the presence of a virus.

If your computer has become unstable, that's a sign that something's wrong. Some malware interfer with important files that keep your computer functioning pproperly.
If your computer crashes when you try to run an application or open a file, it means that something has corrupted the data.
your computer seem to run much more slowly than it used to, if this is not the result of running a resource-heavy application, you might have a computer virus.

If you can't access certain drives on your computer, it indicates that something is wrong.
If you notice that file sizes are fluctuating even if you aren't accessing those files.
If you access menus and their appearance is odd or distorted, you could be the victim of a malware attack.