Groups that have used maritime terrorism include anti-Castro organizations, the Provisional Irish Republican Army, the Polisario Front (fighting Morocco for the independence of the former Spanish Sahara), the Moro National Liberation Front (Philippino Moslem separatist group), the Contras, and Palestinian groups. Maritime terrorist attacks compose a small proportion of the total number of terrorist attacks, and the damage caused by such attacks has been small. The attacks have not been conducive to significant publicity. Some attacks have held symbolic value to the attackers over and above their actual value in terms of money and publicity. There is apparently a significant degree of state involvement in maritime terrorism, without which the surrogate terrorist groups would lack the resources and know-how to conduct the attacks. Overall, maritime terrorism is a persistent, low-level threat, but it has the potential of being a high-level threat.