Tamara has an excellent post (cross-post, I guess) up titled "On RUMINT".
As a former secret-squirrel type, I cannot recommend this highly enough.
In the SIGINT world, we used to indicate phrases we weren't sure of in our gist by indicating the validity of a word or phrase by writing "(%A VAL)" or "(%B VAL)" after it.
Most of the rumors I'm hearing these days amount to about a %Q VAL.
No, the Stafford Act does not give the president the authority to declare martial law.
No, the National Guard is not being Federalized and mobilized to enforce lock down nation-wide.
If you heard it from a friend who heard it from a friend... it's probably BS.