Real time : Avira Free Antivirus On demand : HitmanPro Addon : Chromium (µBlock+HTTPS Everywhere) / Firefox (Adguard+HTTPS Everywhere)
Avira Free Antivirus is very light on my system (when I was testing) and my gf system (she still using it).There is no tricky feature in it. Privacy is acceptable for free version(the best on free area). HitmanPro with no installing and only weekly scans. You can use all filters in these adblockers for your privacy and tracking problems (or your other needs). HTTPS Everywhere is one of the best extension for all browsers.
Hello everyone, nice to meet you again,
For me The Lightest Security Setup 2015 is Webroot (Webroot Secure Anywhere) AV (WSAV)
ESET version 8.0.304 CPU Resources 100MB