Apple has released a field guide for avoiding and removing the MacDefender scam anti-virus malware.
For those of you lucky enough not to have encountered it, MacDefender is a real looking pop up web advertisement that tricks unsuspecting users into believing that their Mac is infected with a number of viruses. By clicking Remove, you’ll actually download (and if you’ve got Safari set up to automatically open downloaded files, initiate the installation of) MacDefender’s extortion malware. MacDefender adopts that classic mafioso protection scheme of ‘pay me or else’, flooding users’ screens with graphic pornography at random intervals unless they pay for ‘protection’.
You can find Apple’s guide to avoiding and removing MacDefender here. Look out for a patch in Software update soon to automate the removal/avoidance process. And as always, never enter your administrator password unless you know exactly what you’re doing or installing. If you’re not sure, call someone who is before you do. That’s the only anti-virus you’ll likely ever need for your Mac.