I understand that the RN had very little confidence that they could shootdown an Exocet. They assigned a helicopter to hover astern of each carrier to serve as a last ditch defense against an Exocet attack. The Helicopter was to interpose itself between the missile, and the ship, and take the hit. How they could actually do that isn't too clear to me, but they were to try to do it, and give up their lives for their fellow sailors. Prince Randy Andy was one of the pilots taking his turn on suicide guard duty. It struck at the time that this was the technological state the mighty RN had been reduced to. Just stunning.
At least today the RN has much better point defenses. At least that's progress. In many ways the Falklands was both a high, and low point for the British Military. I still can't believe that the RN has only 19 major surface combatants. Their new carriers will keep them in the power projection game, and their SSN's, and SSBN's still make them a major naval power, but the decline since WWII is still jarring.
The helicopter was fitted with a radar transponder which made it look like a BIG target, they would fire a chaff pattern to the left of the ship relative to the missile bearing as EXOCET would always start scanning from left to right and then move away from the chaff pattern to the right, the helo would remain between the ship and chaff pattern to further confuse the missile. The helo would then climb and confuse the missile further if it locked on to the helo, the risk of being killed by a EXOCET was very low for the helicopter crew.
The RN were fully aware of the shortcomings of EXOCET and various countermeasures. The Sheffield was lost as the ship was not running its radar as it interfered with the SATCOM so they got no warning of the incoming missile. The Atlantic Conveyor which was killed had no chaff or EW system, this is why it was hit.
USN WWII tactic called "banzai jamming" for obvious reasons. Off Okinawa it took two forms, the inner destroyers assigned were to interpose between the Japanese inbounds and FLAK trap and be the bomb and torpedo sponge. The outer destroyers, the pickets, were to radiate and make noises like an aircraft carrier to buy the CAP time to vector in.
In the 1950s when helicopters joined various fleets, it became standard with the French and Americans to assign suicide decoy duty to their helos as the cruise missile came into service. The chaffe rocket launchers were a 60s development invented by Sweden and Israel (and the US in imitation.)
In modern conditions, it is best to decoy and seduce with countermeasures. If you are in the RAM, Goalkeeper, Phalanx regime and you are relying on those systems in that part of the fight, you will be swimming with the sharks.
Isn't the issue of Blue on Blue more a failure of IFF?
I think that is a fair statement. More than one military (most of them) seems to have trouble with it, so it should be an expected incident of war, not to be confused with probability of hit/kill in engagement contexts.
But to keep this in army contexts...
Dummies and decoys.
Armies need to remember that old campfire trick the US 2nd cavalry used to use on Native Americans. Not enough attention is paid to deception practices and gear. I'm reminded of that English magician who "moved" Alexandria about 30 kilometers and foiled both the Regia Aeronautica and Luftwaffe, or Montgomery's tricks at El Alamein or Fortitude at D-day. Rubber tanks and trucks and soldiers using loudspeakers and phonograph records or driving jeeps to make fake tank traps or digging fake latrines may not seem like much, but Gull I. Bull on the other side has historically fallen for cheap trick ruses over and over again. Naval decoys applied to land warfare have some anti-guided artillery ordnance uses for example.