You saw “Captain Phillips” too!
On a serious note, the only meaningful way to protect tankers is a naval escort with anti-ballistic missiles.
Ballistic missiles are not the problem
Small anti ship missiles and other suck rockets having short range are the risk. The navy vessels contain armament specifically designed for defense against such weapons.
Mines are to my surprise a potential problem as well. I think our navy can insure a clear unmined path
Our air forces are attempting to destroy the sources of such attack but apparently have not yet completed the task.