The best way to detect unauthorized copies of licensed software on systems is to conduct periodic software scanning. This involves running scans of the systems for any unauthorized software that may exist, and identifying any software that doesn't match the list of authorized software. This process should be done regularly and should include any software that is licensed for use on the systems. Additionally, controls should be implemented to prohibit downloads of unauthorized software and senior management approval should be required when installing licenses. Periodic counting of licenses is also important, but is not the best way to detect unauthorized copies of software.