This story is not very old, definitely less than 20 years, so it is not the same as
1970s novel about computer hackers extorting a city
though the theme is the same. But it is not just a city. I think that they take hostages the computer systems of most of the big companies in the world. The amount asked for each company is quite reasonable and they would all agree to pay. But there is a hitch: the ransom has to be paid in virtual money, of course, maybe called bitcoins, maybe a different name. And it has to be brought "physically" at a specific "position" in a virtual world. Which means that all kind of thieves are waiting in ambush to steal the money brought there, the total of which is enormous. Each company has to hire "shotgun riders", hackers who can keep thieves away, for amounts much higher than the ransom asked by the original hackers, some make "convoys" to share expenses...
There are many more themes mixed in, but I don't remember anything else.