Pirates have a new weapon.

A global shipping company noticed that over the course of several months last year, pirates armed with guns had been rummaging through cargo more quickly than usual before making off with the most valuable crates.

When one unnamed shipping company hired Verizon’s VZ, -0.39% security team to investigate, they learned the pirates had begun practicing another trade: Hacking.

Verizon described the hack in its annual data breach postmortem released Tuesday.

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“Rather than spending days holding boats and their crew hostage while they rummaged through the cargo, these pirates began to attack shipping vessels in an extremely targeted and timely fashion,” the report said. “Specifically, they would board a shipping vessel, force the crew into one area and within a short amount of time they would depart.”

And these modern day pirates seemed to know exactly where to find their loot. “When crews eventually left their safe rooms hours later, it was to find that the pirates had headed straight for certain cargo containers,” the report added. “It became apparent to the shipping company that the pirates had specific knowledge of the contents of each of the shipping crates being moved.”

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So how did these pirates of the high seas know exactly what ships to invade and where to go once they had gotten onboard and taken the crew hostage? “They’d board a vessel, locate by bar code specific sought-after crates containing valuables, steal the contents of that crate—and that crate only—and then depart the vessel without further incident,” the report said. “Fast, clean and easy.”

According to Verizon, the pirates-turned-hackers found a way to see merchandise details in the records carriers release — and to see which vessels were scheduled to carry it. (For a more technical explanation of their attack, see page 55 of the report.) So they helped the shipping company shut down severs the pirates had compromised and build a security plan.