The best free security software?

What are the best free security software? (ie. spyware, antivirus, firewall, registry cleaner etc.)

The best free security software?symantic

Ubuntu Linux

The best free security software?viruses

I'll provide you with top 3 in each category

antivirus

1. avira antivir classic

2. avast home edition

3. moon secure antivirus

antispyware

1. spybot search and destroy

2. spywareblaster

3. 1-2-3 spyware free

HIPS

1. threatfire free

2. COMODO antimalware

3. winpatrol free

FIREWALL

1. online armor free

2. comodo firewall pro

3. kerio personal firewall 4

Other tools:

ccleaner, hijackthis, sandboxie.

personally, I would suggest avira antivir, threatfire free, spywareblaster, kerio personal firewall 4 with sandboxie and ccleaner. It boils down to a matter of personal preference.
this requires an opinionated answer. i have used avg free antivirus and zonealarm free firewall for many years now and have always been happy with their performance. they can both be found at download.com. i've always been a fan of adaware for adware removal until their most recent update. i recently started using superantispyware (free version) and it seems to work very well. it can also be found at download.com