There is now an Internet-based piece of malware that affects Macs. It's not a virus, as it relies on you to give it the okay to install itself and begin its malicious purpose: annoy you with pop-ups and false security threats until you give it your credit card number so it can "fix" the problems. Your credit card number is then stolen.
It disguises itself in hijacked ads on legitimate websites (just like its cousins that affect Windows computers) and pretends to scan your computer and find problems. It will then download a file to your computer and prompt you to enter your password.
To prevent bad things from happening to you, please do the following:
• Do not believe anything telling you that your computer is infected. Simply quit your web browser.
• Prevent unwanted files from automatically opening on your machine:
1. Open Safari, select Safari:Preferences.
2. In the General tab, look for a checkbox that says "Open safe files after downloading." If it is checked, anything you download will be opened automatically. This is convenient when you're downloading pictures, videos and documents, but is unfortunately the modern equivalent of leaving your front door unlocked and hanging wide open. 3. Uncheck that box, then close the preference window!