swh,
Any software can be defeated. Just by having something in place will stop most attacks. If someone wants in your system and you are on the Internet, they will get in. It is that simple.
The good news is hackers do not want access to home PCs. They are after large corporations and government networks.
The point is, nothing is perfect, but by having either a Hardware or a Software Firewall, you are reasonably safe.
Take Care,
Richard