In the MedStar incident, patient data was not compromised. But a ransom note indicated that MedStar was the victim of a ransomware attack, in which files are encrypted and held hostage for money. Hospitals in California and Kentucky have also fallen prey to recent ransomware attacks. In MedStar's case, the hackers demanded payment in the hard-to-trace digital currency bitcoin in exchange for the digital keys to unlock the encrypted data. The health system, which owns 10 hospitals in Washington and Maryland, including four in Baltimore, has said it did not pay a ransom to anyone.