An old trick is being repackaged for Macs. A malicious program purporting to be an anti-virus program called MacDefender has been circulating around the Internet in the last few days and targeting Macs (this is why we recommend iAntivirus or ClamXAV for all Mac users). Make sure to be careful about downloading software from websites that you don't know and trust.
I anticipate that you will see many e-mails and websites in the next few days that include attachments claiming to be video of the assassination of Osama bin Laden. Please don't open any videos that are not posted to legitimate news sites.
For more information about these recent attacks, please take a look at these articles.