You can’t protect your machine with only an antivirus. They can’t save your system from unauthorized access through networks. You need firewall softwares to block these types of network attacks and allow authorized access of your machine.
For that reason, the security trio continues..
A good collection of free firewall software downloads is listed here. Some of them may be popular and others may be new to you.
Ashampoo
http://www2.ashampoo.com/webcache/html/1/product_2_0050___USD.htm
Comodo
http://personalfirewall.comodo.com/download_firewall.html
Online Armor Free
http://www.tallemu.com/free-firewall-protection-software.html
PC tools
http://www.pctools.com/firewall/
Privacyware
http://www.privacyware.com/personal_firewall.html
Sunbelt Personal Firewall
http://www.sunbeltsoftware.com/Home-Home-Office/Sunbelt-Personal-Firewall/
Web Root Outpost
http://www.webroot.com/En_US/consumer-products-desktopfirewall.html
Zone Alarm
http://www.zonealarm.com/security/en-us/free-upgrade-security-suite-zonealarm-firewall.htm
Wait..
If you want to test any firewall from the above, please visit the following link. http://www.auditmypc.com/firewall-test.asp