First I want to start by saying over the years I have used various anti virus programs. Some programs have been great, some free, some with a lot of holes. I am now using Kaspersky personal version and I have been happy. I am in no way advising you to buy this brand of security but I will say it works for me and I am on a lot.
OK here are some good pages to look at about Kaspersky: http://usa.kaspersky.com/about/how-we-work/principles-of-fighting-cyberthreats/:
More to read: http://usa.kaspersky.com/about/how-we-work/cooperation-with-governments-and-law-enforcement-agencies/
There is a lot more. On my version I often choose to run a quick scan it is much faster and it looks at important areas of your computer. A full scan of my system can take over an hour so I usually will run this after business hours. What ever you choose you must have some form of virus protection and this one is not that expensive to buy. I will be looking at others soon.
One last thing, read this about an overview of Kyspersky it may allow you to think as to why you should choose them: http://usa.kaspersky.com/about-us/company-overview/
More to come.