If you still want to run antivirus for some reason, ClamXav (which is free) is one of the best choices, since it isn't a resource hog, detects both Mac and Windows malware and doesn't run with elevated privileges.

While you may elect to use it, 3rd party antivirus software is not required to keep your Mac malware-free. That's all you need to do to keep your Mac completely free of any Mac OS X malware that has ever been released into the wild. For other software, it's safer to get updates from the developer's site or from the menu item 'Check for updates', rather than installing from any notification window that pops up while you're surfing the web. Use Software Update for your Mac software. Always keep your Mac and application software updated.For added security, make sure all network, email, financial and other important passwords are long and complex, including upper and lower case letters, numbers and special characters.Don't open files that you receive from unknown or untrusted sources.Never let someone else have access to install anything on your Mac.If you're not sure about an app, ask in this forum before installing. Be careful to only install software from trusted, reputable sites.Change your DNS servers to OpenDNS servers by reading this.(This is not to be confused with JavaScript, which you should leave enabled.)

Leave Java disabled until you visit a trusted site that requires it, then re-enable only for the duration of your visit to that site. This will protect you from malware that exploits Java in your browser, including the recent Flashback trojan. Disable Java in your browser ( Safari, Chrome, Firefox).Uncheck 'Open 'safe' files after downloading' in Safari > Preferences > General.Make sure your built-in Mac firewall is enabled in System Preferences > Security > Firewall.

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