Methods, systems, and apparatus, including computer program products, for secure authentication for accessing remote resources are disclosed. In some implementations, a user is authenticated for a first time on an interface using a first communications channel; the user is authenticated a second time on the interface using a second communications channel; access privileges are determined based on authenticating the user for the second time; and a random Uniform Resource Locator (URL) is generated based on the access privileges, where the random URL is single-use and indirectly associated with a requested resource.