If you use the internet even just for email and Facebook you should have some type of Antivirus software. There is no reason to go without antivirus these days. Antivirus software will protect your computer against all sorts of threats. On top of protecting against malicious software, it also protects against many other computer hazards such as email scams, ransomware, web site pop-ups and redirects to malicious sites. On our own computer systems we use Trend Micro Antivirus because it offers reliable antivirus that will protect you from just about anything you come across in your web browsing.
Comparing Trend Micro to Norton (one of the largest antivirus providers), Trend Micros standard antivirus package provides more protection, where Norton doesn’t protect you against ransomware or email phishing scams, Trend Micro does.
Here's a quick comparison to look at:
Some other options are:
Bitdefender Antivirus Free
Microsoft Windows Defender