There's often a misconception about what type of information is classified in the realms of military aviation.  The vast majority of the systems are unclassified albeit restricted, while classified systems (confidential and above) are similar to those found in 4th gen fighters, that is to say very few e.g:   
1) ECM and jammer modes and performance 
2) Radar Performance (e.g detection ranges, look down performance, ECCM capabilities and few operational modes) 
3) Weapon systems performance (e.g detection ranges, ECCM capabilities, kinematic performance, fuzing, explosive effectiveness and on occasion a few weapon system modes)