In the West, we are accustomed to nationally directed defence/warfare but that may not apply in the ME. For a start, religion remains a serious issue and culling infidels (of whatever persuasion) is a worthwhile objective on the path to heaven and all those virgins. So there may be Shia groups loosely affiliated to Iran happy to harass the infidels using whatever means they can lay their hands on, hence the drone attacks. Even though the damage inflicted to date has been minor, it is the overt threat that will raise insurance rates and deter ship owners from putting their vessels and crews in harm’s way.
Provided no Iranian vessels or oil are targeted, the hazard helps Iran, so Iranian counter-measures are likely to be either non-existent or purely window-dressing. It is difficult to defend against drones whether aerial or seaborne and the cost of a missile will be many times that of the target.
The conventional `solution’ would be to attack the bases from which the drones originate, but they don’t require fixed facilities and can be controlled from anywhere along the coast. Even more importantly, the bases will be on Iranian territory and an attack on the bases is therefore an attack on Iran.
A far better answer is to equip the ships with counter-measures and presumably some form of electronic interference with the drone’s navigational/communication software might be the answer. Each ship could then perhaps be enclose in an electronic noise bubble into which drones cannot penetrate. As this might possibly also mess up the ship’s own navigational controls, we could get back to the heroic days and captains will once again pace about shooting the stars with their sextants rather that watching