My mother says:
In the school where she works, the FSBshnik came, such as to check the readiness to repel a terrorist attack. Naturally, without warning anyone in advance, he went to school with a yellow bag with a bomb in it, passed past the guard, walked down the floors, went down again and left the bag right next to the guard.
Having found out that the school was completely offended by a potential terrorist attack, the FSBshnik went to arrange a discharge to the leadership.
And while he was walking, the package with the "bomb" saved safely :-R
Now the whole school together with the FSB is looking for an underrating device xD