Defenseless?? They are the most heavily armed Anti Submarine Vessel in the world, both hull mounted and towed Sonar.
3 ASW rocket launchers and both ASW Torpedoes and ASW Missiles, both conventional and nuclear armed.
They also have 3 ASW Helicopters with dipping Sonar, sonobuoys and MAD and armed with Torpedoes, Mines and bombs.
So No, they are in no way defenseless, one of its main objective is to hunt Submarines.