What’s the going rate for a human life? Depending on a hostage’s citizenship, their employer, and their personal wealth, the ransom asked for can climb into the millions. Half a million is good money in a country with a per capita annual income of $600. Piracy, so often relegated to history books or theme-park inspired movies, is a real phenomenon. It’s deadly, risky, ancient, and with the advent of completely crewless autonomous ships, might radically change in the future.

Naval patrols are a limited resource, and the oceans are vast. Rather than finding and tracking pirates where they are, future ships could simply deny them their easiest mark: the people on board.

How Things Stand

Last year, an Al Jazeera investigation found that the government of Italy to free hostages. Some of these were reporters and Italian nationals captured while working in Syria. In another case, were captured by pirates off Somalia in 2010 and held until Italy paid $525,000 for their release in 2012.

There were 246 pirate attacks in 2015, 445 attacks in 2010, just 279 in 2005, and 469 in 2000, according to the . Where the attacks take place shifts: in 2000, just five percent of attacks took place in the sea near , but in 2009, over half of pirate attacks took place there.

Naval patrols adapt, focusing on dangerous spaces to protect the vessels coming through, which gives pirates in other parts of the world more room to adapt and attack. In 2016, it’s Nigeria that’s seeing an uptick in piracy, with at least one .

Maritime commerce is the best, most cost-effective way to move lots of stuff long distances. And like the first steps towards driverless cars on land, companies are starting to imagine ships without crews. Or with crews, but remote ones, who oversee the boat by satellite and control it from consoles safely on land.

Naturally, the plans for autonomous ships aren’t primarily about security. Instead, they’re cost-savings schemes. Sailors cost money, and because of their inconvenient needs like a place to sleep and a place to eat and a place to use the toilet (not, ideally, the same place), sailors take up space that could instead fit more cargo. They can also get held hostage until a ransom is paid to their kidnappers, which even the most unfeeling shipping company can acknowledge is at least expensive and inconvenient.

With this in mind, Rolls Royce PLC (not the car company) envisions future cargo liners . Removing the crew from the ship should translate into cheaper operating costs, and could even reduce the numbers of accidents . The ships wouldn’t be entirely unmonitored, with supervising humans tracking their progress on land and sensors in the vessels to any problems on board.

This is a concept for the future: putting in place the satellites, autonomous ships, remote monitoring, and drone stations to inspect underway vessels is the work of years, if not decades. Many of the technologies exist in an early form, from DARPA’s autonomous ships to the growing satellite constellations that orbit earth. But none of it means anything if the future vessels get hacked.

This week, cybersecurity professionals and hackers across the world are gathering at Defcon in las Vegas, where they’ll present the latest evidence that a system being hacked isn’t a matter of if, but of when.Here are three ideas about what piracy will look like when ships do not have human crews.

The Cargo Becomes The Hostage And The Threat

Demanding ransom works because people are much more willing to pay for unique, irreplaceable lives than they are for replaceable, inanimatethings. But explosives are cheap, and without people on board to fight them off, a future pirate crew could potentially board a ship and place explosives on it, demanding a fee for disarming the bombs. If they do this in a narrow shipping lane, then suddenly an exploding ship becomes everyone’s problem.

The downside is that, rather than moving human hostages ashore where they can be held until the ransom is paid, the bomb-placing pirates still have to hold the ship, putting them at greater risk for a cargo that’s less valuable than the hostages they’re used to taking.

Attacks like this are mostly the , though not entirely. Setting off bombs on ships was a regular tactic for , and in 2003, attackers with bombs and axes help British and American nationals hostage on an . And in 2008, Somalia pirates seeking a higher ransom , sending cargo and crew to the depths unless a greater ransom was paid.

If the ship is remotely controlled and communicating with satellites, that means hacking could play a role in future piracy at sea. “Spoofing” is a technique that sends different GPS coordinates to a vehicle, with the aim of throwing it off course.

Rather than a hostile attempt to crack into a computer system, spoofing simply tries to feed GPS readers incorrect information. And we don’t have to imagine what it would take to spoof a ship: in 2013, a team of researchers from the University of Texas at Austin already did it, deceiving the , sending it hundreds of meters off course.

Like the previous example, pirates that redirect a ship could send it somewhere until a ransom is paid, or they could crash it into rocky shoals if the ransom isn’t paid.

Making a ship crash this way is likely easier than redirecting it, but either way it would take some skill and technical sophistication, much more than just climbing aboard a ship with a gun.

People are still the easiest mark in the sea. Cargo ships and tankers are attractive targets because they have relatively small crews and are operated by wealthy companies, likely to pay for ransom or encourage a government to do so. With the people removed from those vessels, the safest bet is that pirates will switch to finding ships with people on them instead.

In 2015, bulk carriers , while fishing ships were only attacked twice, and passenger ships and yachts each only attacked once.

(As an aside: In 1974, former Yankee Gerry Priddy was of attempting to extort a cruise liner. He claimed there were bombs on board the Island Princess,” and demanded $250,000 to reveal the location of the bombs. That’s roughly $1.3 million in 2016 money. The crew searched the ship, found two small, unmarked packages, and tossed them overboard. Extortion works a lot better when the threat is real.)

Without people to rob and ransom on big cargo ships, I’d expect pirates to move to attacks on smaller vessels, and ones whose explicit purpose is carrying people.

So what’s the most likely danger of replacing sailors with robots? A shift in pirate attacks to people who are traveling the sea for fun, not business.

is a defense journalist who has . His work regularly appears at , and he edits even nerdier stories at . He is as interested in the future of war as he is uninterested in actually calling them UAVs, not drones.