Кошка
скрывается под диваном. != Кошка
прячется под диваном.
As similiar as those sentences look, there would be a difference in the
point of view they convey.
The first sentence means that
you as a person is looking for a cat. You don't know where the cat is. Assume that cat is doing nothing. So the sofa is a barrier between you and the cat. To find a cat
you need to look under the sofa. So the first sentence could be an answer to the question "Where is the cat?"
"The second sentence means that the
cat is doing some effort in
actively hiding from you. It knows that you're out there so it would find its place under the sofa as a reliable refuge.
Now, the reason the spies are not hiding (прячутся) is not because they don't
but because it's impolite to the spies which are respectful persons. However, when being applied to unlawful persons such as thieves both usages are correct depending on how formal you are:
Вор прячется от закона.
Вор скрывается от закона.