If you've seen a genuine article being vandalised, don't edit the change out unless it's minor or you have new information to add. Instead, edit a previous, non-vandalised version from the history or roll the article back to that edit - this way, information doesn't have to be constantly republished.
For cases of major vandalism or new articles being created with spam content, please post on User_talk:TeamCodex with the offending article so it can be brought to a Moderator's attention, if you cannot deal with it yourself.