Crooks have hacked the European Central Bank's website, stealing contact data and demanding a ransom for its return.
In a statement, the ECB says that the security protecting a database was breached, leading to the theft of email addresses and other contact information left by people registering for events at the bank.
The theft only came to light when the bank received an anonymous email "seeking financial compensation for the data".
Most of the information was encrypted but parts of the database included email addresses, some street addresses and phone numbers that were not.
The database is physically separate from any internal systems, so no market sensitive information was compromised, says the bank.
The German police have been called in and people whose email addresses or other data might have been compromised are being contacted, while all passwords have been changed.