Realistically - NO.
There are a few virus that affect MicrosoftWord documents but you can prevent those by disabling Macros when loading unfamiliar .docs files.
As for spyware, there is none that is downloaded and installed automatically via the internet.
Some people have written programs that 'phone home' with information, and for that I use a program called Little Snitch. It is like a reverse firewall.
But in general, Mac OS X is fairly safe though design and obscurity. Plus many of the security features are on by default.
So at this time, there is no need for either type of software.
Please keep in mind that many of thr mac antivirus programs actually allow more problems to happen than if you had none.
As for a buffer overflow, no virus program will manage this, this is better handled by your ISP or a good home firewall/router.