Do I need a firewall and where can I get one?

With all theses malwares ,viruses etc firewalls are absolutely necessary if you use a broadband connection (DSL, Cable, Satellite, etc.). Their aim is to protect you from intrusion and attack from others on the Internet. If you have Windows XP or Vista there is a built in firewall you can use. If not, you can download the free version of Zone Alarm at:
http://www.zonealarm.com/security/en-us/zonealarm-pc-security-free-firewall.htm
Note that,nowadays free firewall software are quite scarce , most of them are now licensed, among the free ones you can still get:
Kerio Personal Firewall (KPF)
NetDefender