I believe casinos track and monitor player bankrolls through a combination of technology, surveillance, and personnel. They use systems to monitor and analyze player activity, including betting patterns, transaction history, and account balances. This information is used to identify suspicious activity, detect potential money laundering, and ensure regulatory compliance. Casinos also train their staff to recognize and report unusual behavior, and they collaborate with regulatory bodies to share intelligence and best practices. By actively monitoring player bankrolls, casinos can maintain a secure and compliant gaming environment.