What does 'spook credentials' mean?

Solution 1:

'Spook' (an informal word for a ghost or spirit) is also a mainly US English slang word for a spy, secret agent, etc. To have credentials in something means to have qualifications, experience or knowledge in that field. Both named men were members of the US government intelligence community.

spook noun [C] (PERSON) slang

spy

Spook (Cambridge Dictionary)

credentials

noun [ plural ] abilities and experience that make someone suitable for a particular job or activity:

business/educational/professional credentials

He is keen for people to know his business credentials.

Credentials (Cambridge Dictionary)