Q: What are the limitations of an antivirus in protecting a PC?
A: First and foremost is an antivirus (anti-malware) is limited to protecting against only malware. Malware is just a minor player in the cybersecurity arena.
They are limited to protecting only against the malware they have been designed to recognize. Even the very best protect against perhaps 99.9% of known malware. Depending on whose numbers you believe, there may be more than 100,000,000 malware in the wild. That leaves at least 10,000 known malware even the very best don’t protect against.
As to how many unknown malware are in the wild? Nobody knows.
And then when they come up against malware they know about, they are limited in how well they eliminate the threat, and limited in saving any damaged data – or preventing data from being harvested.
A solution that works more reliably than antivirus is application whitelisting – specifying which applications may run. Then, should malicious code find its way into your device and attempt to run, it is automatically blocked as unauthorized.
Once the malware issue is dealt with, then you can turn your attention to the other security and privacy issues your device faces; email hacking, instant message hacking, phone call monitoring, man in the middle attacks (notice women rarely get in the middle of this) (sorry, it had to be said and I was just standing around), social media (it’s own kind of malware), storage device encryption, Multi-Factor Authentication, Disaster Recovery and Business Continuity Planning, etc.