Antivirus Software
BitDefender
BitDefender is build by a Romanian company headquartered in Belgrade. We currently use BitDefender because it's one of the top-rated antivirus programs while also being one of the least resource-intensive a/v programs out there.
Update 2020-02-06: A few months into using it on my own computer I ran into a windows bootup problem. Luckily I was able to restore to a previous state, however, I strongly suspected that BitDefender's advanced protection mechanisms were the culprit. So I switched to ESET...for a year. During this year I deployed BitDefender on 30+ computers and did not run into similar problems on any of them. ESET however did give me trouble on my own computer (see below).
ESET
Our runner-up was ESET, a product of Slovakia. Eset is also very highly rated and light on resources, and focuses on being an antivirus program, which is great.
Update 2020-02-06: I personally used it for all of 2019 and only after a year. During this time my PC started "hanging" - the browser, email, other apps that use the internet occasionally didn't respond for 1-2 minutes. This happened particularly when I connected/disconnected from VPN, or resumed my computer, or changes networks. Although I suspected ESET, only at the start of 2020 did I finally find time to remove ESET. Lo and behold, the freezes stopped.
Additionally, I set ESET to add firewall rules interactively. Unfortunately this did not work reliably. It was difficult to exclude a program, and the firewall would flag the same traffic again and again despite me already adding a rule for it.
So do I recommend ESET? Unfortunately no.
Avira
We also tried Avire at some point in time, seems nice enough. Can't remember why we uninstalled it...too high on system resources perhaps?
Kaspersky
We used Kaspersky for all of 2018. The free version is great and very highly rated, unfortunately it's not possible to turn off SSL certificate swapping (necessary for it to scan https traffic). This got in the way of checking whether we correctly deployed updated Letsencrypt certificates for our own sites, because Kaspersky would keep loading its own certificate in place of ours.
We considered the paid option, but during our research we learned of various allegations about Kaspersky having close ties with the Russian government. Maybe these allegations are unfounded, maybe not, in any case we looked around some more.
Avast
Before Kaspersky, we were big fans of Avast, until they started showing too many annoying pop-up ads for their various products. True, we were using the free version and perhaps the paid version shows fewer ads, but in any case we decided to try some others.
