Stick with Defender or Symantec Endpoint Protection, and mbam on demand with good firewall rules for your server. Avoid crap made for clients. Just my 2 shells.
uninstalled it before you could say knife. it even asked me if i knew how to ùpgrade`to w 10! as if i want to know! i took some time and trouble to explain what is wrong with the stuff, since they asked. no good. not more than 400 letters allowed. and i needed a hell of a lot more than that.. so; the morale; NOT repeat NOT recommended! just my 2 cents. seems the stuff is still running, btw, even after uninstall.. time for a reboot.. EDIT: winpatrol warned me of new startup, only after i unnistalled and rebooted.. some glass thing.. not on..
Avast! Avast (NEVER INSTALL ANY TOOLS!) works great on old/slow AND new machines! After MS dropped the ball on MSE..... Avast! It works AND it's free!
I have used Microsoft Security Essentials or Windows Defender for years with great results. They have kept my PC virus free. It also depends on your actions using your PC. Our internet provider offers Kaspersky 2016 for free, but I don't use that, slows my system down too much. Here a couple of recent news stories about anti-virus companies that are very interesting. Google the story titles for links to the articles. "Security wares like Kaspersky AV can make you more vulnerable to attacks" - Sep 23, 2015 - by ars technica "AVG Antivirus Plans to Collect & Sell Your Personal Data to Advertisers" - Sep 19, 2015 - by The Hacker News