In various aspects, a data transfer discovery and analysis system may query an entity computing system to identify access credentials for third-party computing systems and scan each access credential to determine associated permissions provided by each access credential on the entity computing system. The data transfer discovery and analysis system may further inspect access logs to identify actual data transfers between the entity computing system and third-party computing systems as well as other access activity associated with each of the credentials. The system can generate and store a mapping of all actual data transfers (e.g., based on the access log data) and potential data transfers (e.g., based on particular access permissions) between/among the entity computing system and the third-party computing systems. By analyzing access logs to determine actual data transfers executed under each particular access credential, the data transfer discovery and analysis system can identify unused and/or underutilized access permissions.