The role of a system in a network may be categorized as a networking system, a security system, a systems management system, a mail system, a database system, a web system, a file/print system, a communication and collaboration system, and/or any other system in the network. The role of a target system may be determined by sending test probes to one or more systems in a target network. The test probes may be data packets crafted to produce a particular response from a target system. The received responses may be compared to signature responses of a basis system with known operating system, services, and/or roles. By matching the received responses with signature responses, a role resolver may associate a role with the target system.