Tips for OSX security when using public WiFi.
[1] Setup & configure a separate user account named "wifi", heavily restrict this users access rights in the user accounts panel. Restrict every application apart from the ones likely to be used on the wifi, e.g. Mail.app / Thunderbird etc.
[2] Use an alternative Browser; Opera, Camino, FireFox etc.
[3] Turn the Firewall on, with max settings, with everything restricted, and allow connections were appropriate. also enter the advance pane and check settings like "Stealth Mode" etc.
Taking such steps when using public open WiFi we greatly limit risk of infection from malware / worms / Viruses etc.
Being in the field of OSX security, i can also confirm that some form of physical access to your computer would have been needed, or input from your self, file downloads, root prompts etc. if you haven’t already done so configure all browsers on your computer NOT to automatically download "safe files" as this can cause grave security issues which could lead to infections such as the one you have mentioned.
My guess is that you were browsing public, open WiFi on your root account using Safari or FF with auto downloads left on, and your firewall turned off. I could be wrong...
Also a little side-note, you sould use these tips for you root account aswell, accept for the first one! and also make sure you have checked the box "Require Password to unlock each secure system preference" from the sercuity pane, Via system preferences.
Kind Regards,
Mark.
