Is it permissible to hack the devices of administrators and supervisors of pornographic websites in order to disable their sites under the pretext of their spreading corruption, vice, and obscenity among Muslims, and is it permissible to hack the visitors of these sites?

There is no harm in destroying pornographic websites; this falls under the category of changing evil. As for the visitors of those websites, they should be advised, enjoined to do good, and forbidden from evil. If they do not respond, then there is no harm upon whoever seeks to change their evil in this manner.