Viruses and spyware don't care about the network medium over which they are transmitted. That is, they don't care if they travel through physical wiring or over wireless connections. The foregoing is actually most applicable to viruses, as spyware programs themselves technically doesn't spread (although infections that carry spyware as their payload certainly can propagate from machine to machine). In terms of protecting against viruses and spyware, implementation of the protection is, for the most part, the same on both wired and wireless networks.

Security hacks/breaches/exploits, however, do vary with the different physical transmission media, and wireless networks have more issues/weaknesses in this regard than do wired networks, because wireless transmissions are easier to intercept/interact with than are hard-wired networks.

If you can be a little more specific as to what types of attacks/defenses you're thinking about, I'm sure we can give you more specific info.

Ahh... I think I see where you're coming from. If you're talking about infections hitting wireless devices such as cell phones and PDAs, then yes- those are very rare at present, but it is expected that they will become more prevalent as cell phones and other messaging devices become more complex and "feature-filled" (because more "features" means more flaws to exploit). Malicious hacking attacks on these devices will become more common as well.