If you have had problems with viruses and malware, one thing you will notice these days that some of them still manage to get through your anti-virus barriers. Just when you though that your PC is already fully protected, you will notice at some point some abnormal behavior such as blue screens or sudden shutdowns occurring.
At this point, many would attribute it to hardware or faulty software. But if you have the chance, do some research or access online scanning services from leading anti-virus software companies. Scan all your hard drives and leave it for a couple of hours. For sure you will be surprised at the various viruses present in your computer and immediately check if you can update the virus definition files to keep your software up to date.
While that would be a good recourse, chances are the viruses will still not be detected. One thing about software manufacturers in the anti-virus category, most of them differ in terms of identifying security risks and viruses that make their way into your computer. Whether they come from careless opening files from storage devices or from online access using your browser, there will always be files that will get through.
If there is one consolation from it all is that not all files are dangerous. Some of them may be cookies or adware and would normally be categorized. This is what separates software these days. They have their own level of threats to which some may be exaggerated.