Networking is what I did for a living. All of these suggestions are valid and there are many other reasons for this as well. However, that being said, my experience with Century Link is that the speeds are very inconsistent depending on the network load at the time. Also suspect is their wi-fi routers we have needed to have ours replaced. Viruses, malware and redundant apps can also cause a problem. As far as the free anti-virus I believe you get what you pay for but that is MHO.