The moles have ties to the CIA.
In part two of the mole-centric three-parter, the mole—or moles, as it were—reveal themselves to be a group of rogue CIA agents. They include CIA Officers Vostanik Sabatino (Erik Palladino), Randall Sharov (Salvator Xuereb), and Kensi's friend from rehab, Sullivan, a.k.a. CIA Officer Ferris.
The intrigue continues!
Watch NCIS: Los Angeles on Sundays at 8/7c on CBS and CBS All Access.