 The IMB reported in October 2007 that Indonesia continued to be the world's most pirate-struck region with 37 attacks since January 2007, though that was an improvement from the same nine-month period in 2006.The 11 September attacks also heightened the perceived threat of terrorism-related piracy, but US Maritime Administration (MARAD) experts distinguish terrorism from piracy, and piracy from shore gangs who rob ships in port.Some observers argue that there is no single problem of violence at sea, but rather a collection of problems, and that different kinds of violence require different defences.