HarryMann
A ship can switch off its AIS transmitter easily and I think most in the Indian Ocean do so. Whether they turn off the satellite transmitter as well as the VHF one, I wonder: there are pros and cons there. I've no doubt the Somali pirate backers (and many other organisations interested in targeting vessels with potentially juicy returns) have access to both. But so do the naval forces in the region. If you turn off the satellite tracking you disappear from the naval forces' screens as well. Sod's Law.