Security in networking?

I'm looking for security for a 4 computer network in a small business.

I need to know about all the security (in really basic terms) that you would need for a small business and need some software to recomend that does all that. any sites that explain everything you need would be greatly appreciated?

oh and i found this site that said something called Nessus is the best security for networks, what exactly is it and does it cover everything i need?

http://sectools.org/

Security in networking?virus protection software

Find a local supplier specializing in small business. You need to look at three areas to secure your network:

1) The perimeter. This means using a firewall between your office network and the outside world. Sonic wall makes some excellent easy to use firewalls with far more functionality than the least expensive products sold by linksys, belkin etc.

2) The individual PC's. You need anti virus, anti spyware/malware software on each PC. Many of these products are difficult to use and or they use a lot of your PC's computing power to protect it leaving little available for the PC to do your work!.. Trend Micro has good products. avg (www.grisoft.com) has inexpensive products with a light footprint on your pc, Microsoft one care is an inexpensive product with a light footprint that even handles backups. Further each license is good for 3 PC's