You do not need "anti-virus software!"
Linux does not need it.
Windows does not, either!
A very brilliant marketing-person ... and may his soul sinter in a hot place
... coined the word "virus" in reference to rogue-programs. It was, as he knew it would be, a very
appealing idea, because in the real-world of human existence "viruses are an established citizen of this planet, to which we are constantly vulnerable, and against which we must constantly and actively defend."
The marketing ($$$) influence of this notion was so
strong that, to this very day, Windows continues to ship to customers with its very-formidable security system turned off!
"Apple, on the other hand, has as-usual 'got it right.'" And, again as-usual, they've made a ton of marketing-mojo from "the obvious."
Here's the bottom-line ... and please note that it applies equally
to Linux, to OS/X, and to Windows:
(1) Do not, ever,
run your computer as an all-powerful user. Rogue programs, by definition, run without
"your consent" ... but they do run "with your privileges and your identity." Computers are merely machines: they know nothing of your awareness or your intent.
(2) You can have any number of accounts on "your" computer. The computer will recognize each one of them as being distinct. If those accounts are not
"all-powerful," it will understand and enforce
the very-simple notion of ownership
: that "you" have more rights to "your stuff" than anyone who is "not you" does. Even if you wear all of the hats in your (one-man?) company, you do not wear them all at the same time.
(3) Backup software is readily available (it's supplied free of charge
on Windows and OS/X...), and external USB/Firewire disk drives are dirt cheap. (Hey, you can buy 'em at department stores.) Backups can occur once-an-hour (say...) and the backup files will be rigorously protected such that "only you" can retrieve them. Windows backup-software will capture not only files, but the entire Registry.
(4) Since the computer is known to be "ignorant," use its ignorant, brutish strength to your advantage.
If you voluntarily limit the capabilities of your account(s) to encompass only the least
of what "this account needs to do," then you can be absolutely certain that the ignorant, but brutishly-strong computer will prove itself more-than-capable of guaranteeing that no
program "running as 'you,' whether with or without 'your' knowledge" will ever be able to exceed
Linux (since the beginning), OS/X (since the beginning), and Windows
(since Windows-NT) have all
been capable of this.