An intelligence scan was a scan done for the purpose of surveilling planets and people of particular interest to intelligence organizations.
In 2368, intelligence scans showed Ambassador Spock and Pardek meeting on a certain street on Romulus, which Data was later able to identify by virtue of the architecture nearby. (TNG: "Unification I")
As of 2379, intelligence scans of the Reman homeworld showed evidence of dilithium mining and heavy weapons construction. (Star Trek Nemesis)