The BlackSuit ransomware gang
https://www.bleepingcomputer.com/news/security/cdk-global-outage-caused-by-blacksuit-ransomware-attack/
The BlackSuit ransomware gang is behind CDK Global's massive IT outage and disruption to car dealerships across North America, according to multiple sources familiar with the matter.
The same sources, who provided information on condition of anonymity, told BleepingComputer that CDK is currently negotiating with the ransomware gang to receive a decryptor and not leak stolen data.