Did you know that both Lion (10.7) and Snow Leopard (10.6) will protect you from known virus and malware threats?
All you have to do is to ensure that the checkbox in System Preferences under Security & Privacy is checked.
Here’s what it should look like in Lion (10.7):
Here’s what if should look like in Snow Leopard (10.6):
See this link from Apple for more info: http://support.apple.com/kb/HT4651
There is a new threat that has surfaced that will try to fool you into installing the Flash Player. Read more about this from this blog. Apple has not yet included a built-in defense for this issue yet, so the best way to combat this threat is to download Flash directly from Adobe’s website, should you need it. Also, if any software you download from the Internet asks you for your password, you should be 100% certain you know what you downloaded, where you downloaded it from, and what it is.
The Mac Observer made a nice little application that checks your Mac’s Xprotect definitions status and allows for a manual update of the virus and malware definitions: http://www.macobserver.com/tmo/article/safe_download_version_adds_manual_definitions_update/