Get the latest armor. Installing up-to-date computer security software can reduce your risk of becoming one of the “nearly 2 million” households victimized by online identity theft each year. Take advantage of free browser upgrades; many offer protection against attacks. If you have an older PC, “get a firewall”; a free one is available at ZoneAlarm.com.
Look before you click. If a pop-up ad tells you to update software, watch out. Deceptive pop-ups can infect your computer with malicious software, causing you to “unwittingly send out spam” to contacts. Security updates should only be downloaded from sites of a reputable software publisher, such as Adobe, McAfee, or Norton.
Back it up. No security system is foolproof, so get an external hard drive and back up all of your data on a regular basis.
Source: Consumer Reports