As such, the mods of their appropriate forum(s) should delete the thread. However, if it's in an already existing thread, then clean out the posts and any replies to the bot/spammer (as needed) and continue the thread as if the spammer/bot wasn't there.
As a regular user, you can report spam posts by clicking the report post button under the offending post(s). It's found underneath each and every post here, and looks a lot like this:

If you are caught replying to a spammer/bot thread, and it's been done in excess, you may be placed on temporary ban, for no more than 24 hours.
In addition, the report posts button should only be used for reporting spammers/bots/trolls/etc. PLEASE do not misuse/abuse this system. Any such actions will be dealt with as they come.