Intent is a necessary element for that charge, at least on the US Federal level. But in any case, completely accidental possession is a defense, meaning, if you have something in your possession without even knowing that it's in your possession, that can be presented as a defense to charges. That would likely be the same when it comes to being an unwitting distributor of copyrighted material via a stealth torrent. Similarly we don't prosecute individuals whose computers are infected with viruses that propagate (and thus illegally access and trespass onto other systems) without the person's knowledge.