I am sure you have heard of MacDefender or MacSecurity or MacProtector or MacGuard installation packages, right? These were malwares for OSX. Newer malware efforts continue.
The original posters question was about the Mac. He added the question about iPad as an afterthought.
You can learn about efforts to remove malware on the Apple Support site.
SecureMac has discovered a new trojan horse in the wild that affects Mac OS X. The trojan horse, trojan.osx.boonana.a, is spreading through social networking sites, including Facebook, disguised as a video.
When a user clicks the infected link, the trojan initially runs as a Java applet, which downloads other files to the computer, including an installer, which launches automatically. When run, the installer modifies system files to bypass the need for passwords, allowing outside access to all files on the system.