The website for Grubman Shire Meiselas & Sacks is down and hackers claim to have 756 gigabytes of data including contracts and personal emails.
A screenshot allegedly of a Madonna contract has been released, and the criminals are demanding payment.
The New York law firm says it has notified its clients and is working with cyber-security experts.
It's not known what sum the hackers are demanding and whether the law firm is negotiating with them. read the rest here