1.
Zonealarm.com : ZoneAlarm Free Antivirus + Firewall 2013 :
Antivirus/Anti-Spyware Engine
Detects and blocks viruses, spyware, Trojan horses, worms, bots, and rootkits.
Two-Way Firewall
Makes your PC invisible to hackers and stops spyware from sending your data out to the Internet.
Advanced Firewall
Monitors programs for suspicious behavior spotting and stopping new attacks that bypass traditional anti-virus protection.
Privacy & Security Toolbar
Provides site check, do not track, Facebook privacy scan, private browsing and more.
Advanced Download Protection
Analyzes downloads and warns you if a download is malicious-stopping it from infecting your PC.
Identity Protection
Monitors your credit and alerts you of changes in your credit files.
Note: ZoneAlarm Free Antivirus + Firewall 2013 supports Windows 8, Windows 7, Windows Vista, and Windows XP.
2. Full Protection:
Antivirus.comodo.com: Defense +, Anti-Virus, Anti-Spyware, Cloud-Aware Security: Instant Cloud Behaviour Analysis, Instant Cloud Scanning, Instant Cloud Whitelist Checking.
3.
Avast.com : Avast free version blocks viruses & spyware and allows assistance from a geek friend.
4.
Free.avg.com : AVG free version detects and stops viruses, threats and malware and great, easy-to-use protection everyone needs.
5.
Avira.com : Avira offers best free antivirus protection against dangerous viruses, worms, Trojans and spyware.
6.
Bitdefender.com : Bitdefender Antivirus Free Edition is the first free antivirus product compatible with Windows 8.
7.
Windows.microsoft.com : Microsoft Security Essentials helps guard your PC against viruses, spyware, and other malicious software.
8.
Unthreat.com : UnThreat Free Antivirus 2013: Compatible with most operating systems including Windows 7 and the new Windows 8.
Key Features:
State-of-the-art Anti-Virus engine
Anti-Spyware protection
Mail cleaner
Script scanner and blocker
Rootkit/Hook protection
ActiveX monitor
Windows startup and logon security
Registry scanner.