The international effort to suppress Somali piracy halted and reversed the increased piracy off the coast of Somalia but at the same time there has been a major increase in attacks in the Straits of Malacca. Big as in a sevenfold increase from 2009 to 2013 (when there were 150 attacks). There was also a jump (to 50 attacks a year) off Nigeria. The big difference is that it was only off Somalia that ships and crews be taken and held for ransom for long periods. Everywhere else the pirates were usually only interested in robbing the crew and stealing anything portable that they could get into their small boats. Off the Nigerian coast pirates occasionally take some ship officers with them to hold for ransom. Another tactic is to turn off tracking devices and force the crew to move small tankers to remote locations where most of the cargo (of oil) can be transferred to another ship and later sold on the black market. But that sort of thing requires a lot of organization, nerve and luck. So most of the attacks are armed robbery. Given the amount of portable electronics on a seagoing ship (both company and personal), a half dozen armed pirates can net several thousand dollars per ship hit. There are fences on shore who pay cash for this stuff and quickly move it out of the country.
It’s not the theft aspect that worries shipping companies using the Malacca Strait, it’s the possibility of terrorists using the pirates or the pirates causing an accident that blocks these vital straits. Piracy in the vital (most of the world's oil exports pass through here) Strait of Malacca has gotten a lot worse and so has the risk for catastrophe.
For the pirates there are lots of targets, with over 50,000 large ships moving through the Strait of Malacca each year. That’s 120-150 a day. Lots of targets. The 800 kilometer long strait is between Malaysia and Indonesia and is 65 kilometers wide at its narrowest and depth are generally 27-37 meters (90-120 feet). The shallow and tricky waters in the strait forces the big ships to go slow enough (under 30 kilometers an hour) for speed boats to catch them. But if there’s a collision, especially one involving a loaded oil tanker, the oil spill could be huge and a large ship sinking in the strait could block or throttle traffic for months.
There’s no easy solution to the piracy in the Strait of Malacca. Pirates usually function on the margins of society, trying to get a cut of the good life in situations where there aren't many options. This is usually in areas where state control is weakest or absent, in failing and "flailed" states. A flailing state is something like Nigeria, Indonesia, or the Philippines, where the government is managing to keep things together but is faced with serious problems with regions that are sometimes out of control. In a failed state there are areas where there isn't much government at all and pirates can do whatever they want most of the time. With the Strait of Malacca the problem is that there are a lot of poor (or not so poor but very ambitious) people in the area with access to boats and experience using them in the ocean. Speeding along next to a huge tanker or container ship at night in the Strait of Malacca and using a grappling hook or very tall ladder to get aboard is not for the faint of heart or anyone with no experience on the water. But as more of these attacks succeed more people are tempted to try and more are doing that.