Bypassing security by injecting malware and viruses into existing trusted delivery systems is the security nightmare scenario. I’ve been advocating for 10 years to reduce your vendor footprint. Producing the number of vendors that you have reduces the number of places that a bad actor can penetrate your systems.
So how do you reduce the number of vendors? Purchase all networking equipment from the same vendor. Purchase and use common software vendors. Even if you hear or feel some software is a little bit better know that in one or two years the situation will probably flip flop. Buying antivirus was adding insult to injury. You would have to pay the antivirus company money for their software, they would install and invade your operating system and then either unwittingly or winningly inject malware onto your computers.