Viruses, spyware, adware and the like all fall under the category of "malware". One of the nice things about Apple's so-called "walled-garden" approach to security for iOS is that you simply can't run software that hasn't been blessed by them.
Despite the mystique that many people seem to associate with malware (viruses), it is software like any other. And since you can't run software other than what is provided by Apple by way of the App Store, you have little to be concerned with. Provided that you choose not to jailbreak the device, you needn't worry about it at all.
You'll notice I edited your thread a bit - please keep in mind that we are a "family friendly" forum. So, if you wouldn't hear it in a Disney movie, it doesn't belong here.
Thanks.