Depends on the User, and by that I mean: what software you are using on top of it and are you taking the necessary precautions when online etc... At the very least, Linux is a better starting point than Windows or MacOSX, as the base system is all open source and, even if you do not have the technical understanding to know what you are looking at, chances are other people with a healthy dose of paranoia have already gone through the code to check if there is any malicious code waiting in there. Can't do anything about hardware embedded microcode, of course, but there are products out there which claim to use as much open source hardware and firmware as possible.