From Symantec:

Norton AntiVirus 2011 protects your PC against the latest viruses, spyware, and other threats. It delivers fast, powerful online protection to keep you a step ahead of cyber attacks. It lets you chat, email and share files without worry, updates automatically, offers easy-to-use features, and includes free customer support during your subscription period.free download antivirus

Norton Reputation Service instantly checks where files came from and how long they've been around to identify and stop new crimeware faster than other, less sophisticated security software. Norton Protection System uses several overlapping layers of protection that work together to stop viruses, spyware and other online attacks. Norton Pulse Updates provides up-to-the-minute updates that protect against the latest threats without slowing down your computer. SONAR 3 Behavioral Protection monitors your PC for suspicious behavior to quickly detect new online threats.free anti virus download