Which threats are characterized by possibly long periods of preparation (years is not uncommon), tremendous financial backing, a large and organized group of attackers, and attempts to subvert insiders or to plant individuals inside a potential target in advance of a planned attack?

Highly structured or planned threat

Explanation:

This type of threat is an highly structured threat that is been planned using every available tools and machineries. The attack of this type consist of three phases, the preparation phase; where all the information and resources needed is been planned and source for. The execution phase; the attackers plane how to carry out the action, the techniques and technology needed for the success of the operation is carried out and tested. The post execution phase; the attackers planned there escape from any trouble that may arise and how not to leave any spot that will make them to be identified.

This type of threat requires to put the security outfit or the entire agency on red alert to ensure effective engagement before the attackers execute their actions.