You dont need anti-virus. Linux , the language of the OS is resistant to viruses. Not to mention that there are few if any viruses coded for linux. If by some remote chance you do get a virus all you have to do is reboot the OS. It is one of the very cool things with Linux, Virus cant get a stable foothold in the system.
Unless they have SU privilages and your password. You can install one that could be hidden in a deep level installing program so you give it permission essentially. With Android since you don't have that privilage yourself unless you root your phone a virus can't really get into your system files. However, they could with considerable trouble conceivably program a virus that could find a way to get access but it is easier said than done and it wouldn't be worth the trouble in general. It is a lot easier to go after microsoft where you can very easily get access to the system files and the 90% Market share makes it a easier more likely target.