FACTBOX - Who are the pirates off Somalia's coast?

(Reuters) - The following are details of the pirates who hijacked a Saudi supertanker with a $100 million (66 million pound) oil cargo, the boldest such attack yet and the culmination of several years' increasing activity.

* HOW DOES IT WORK?

-- The pirates live on "mother ships," storing arms, fuel and other supplies on board. They catch target vessels using high-speed boats, heavily-armed men boarding with rope ladders.

-- Intelligence sources say three trawlers in the Gulf of Aden are believed to be pirate "mother ships."

-- Around three speedboats may be used in an attack, each carrying six to 10 men armed with AK-47 assault rifles and sometimes rocket-propelled grenades.

* MONEY EARNED:

-- Pirates often treat hostages well in the hope of hefty ransoms. Most captured ships have brought ransom payments of more than $10,000 and more recently much more. The larger vessels captured in the busy shipping lanes of the Gulf of Aden fetch on average a ransom of $2m.

-- The money could be invested in trafficking khat, a mild narcotic leaf that is very popular in the region. Banned in many Western countries, khat is a flowering plant that is native to east Africa and the Arabian Peninsula. Users get a mild amphetamine-like high.

-- Residents of Garowe and Bosasso, Puntland's other main town, say most of the hijackers are well known as the wealthy pirates have attained near-celebrity status in the area.