CDK Global, a software provider for auto dealerships in the U.S., has been hacked, forcing a shutdown of most systems and affecting around 15,000 car dealerships. Major clients like General Motors and Group 1 Automotive rely on CDK. While some systems are back online after tests, the company is still working to restore all applications. CDK offers dealerships tools for managing payroll, inventory, and office operations, with cybersecurity solutions advertised on its website. The cyberattack began on Tuesday evening, but the culprit is unknown. Affected dealerships have resorted to using spreadsheets and sticky notes for small transactions, limiting larger sales. The outage has prompted dealership employees to seek alternate ways to conduct business, highlighting their reliance on CDK's systems.