LAIRCM = Large Aircraft Infrared Countermeasures
DIRCM = Directed Infrared Countermeasures
The cluster of sensors and pods (The tail closeup is a smaller version on a C-40 (737) but it is the same concept . The system will detect AND then use lasers or directed IR energy to try to burn out the seeker head on infrared missiles.
The sensor area (cropped pic) is on each engine and it also may be part of the DIRCM system (my assumption) since there is one over each turbine
The USAF really does not talk about the details but it is also rumored to have chaff (for radar missiles) and flares (Ir Decoys) and electronic jamming gear on board.
https://www.dote.osd.mil/Portals/97/pub/reports/FY2011/af/2011laircm.pdf
https://uk.leonardo.com/en/news-and-stories-detail/-/detail/dircm-explained
