US Patent 9906552 Managing system load

System load, such as load caused by a denial of service attack, is managed by requiring those requesting access to the system to provide proof of work. A system receives, from a requestor, a request for access to the system. Before the request can be processed, the system provides a challenge to the requestor. The requestor obtains a solution to the challenge and provides proof of having obtained the solution. The system verifies the correctness of the solution and, if the correct solution is verified, the system services the request.