Please dont fall into the mindset that says free is good - none of the free antivirus can do as good a job as a proprietary one. They just dont have the funding for development or staffing. I can never understand why people will spend hundreds of pounds on a computer and baulk at a few pounds for decent protection. I always use Norton which, properly setup, is untouchable - no virus in 15+ years of use. The latest version offers 2 year packages for about £7 per machine per year - and can include tablets and phones. I have helped many friends / colleagues over the years and a very high percentages of their issues stem from using free antivirus.