A method for operating a telecommunications network, the method comprising: obtaining request records from a domain name server, DNS, of a content delivery network, CDN, the DNS being of a DNS architecture of the CDN; creating a DNS request result file comprising a plurality of domain name addresses and associated plurality of Internet Protocol, IP, addresses at which requested content of the CDN is accessible to a requesting device (104, 204); receiving, at a proxy server, a first DNS request intended for the DNS of the CDN, the first DNS request received from the requesting device and comprising a first domain name address for a requested content; and mitigating against an attack on the CDN comprising: determining whether the first domain name address of the first DNS request is included in the DNS request result file; when the first domain name address of the first DNS request is not included in the DNS request result file: providing, by the proxy server and to the requesting device (104, 204), an IP address comprising an embedded verification value, wherein the first IP address redirects the requesting device back to the proxy server; verifying that the requesting device (104, 204) is a legitimate requestor based on whether the proxy server receives a redirected request for the requested content from the requesting device that includes the embedded verification value; transmitting a redirect instruction to the requesting device (104, 204) that indicates an IP address associated with a hypertext transfer protocol, HTTP, server, wherein the redirect instruction further comprises a designated caching period instruction for the requesting device, the requesting device caching the IP address associated with the HTTP server for the designated caching period; and if a subsequent DNS request is received from the HTTP server, comparing the subsequent DNS request with the first DNS request; and if the subsequent DNS request matches the first DNS request, providing the subsequent DNS request to the DNS and saving a result from the DNS in the DNS request result file. obtaining request records from a domain name server, DNS, of a content delivery network, CDN, the DNS being of a DNS architecture of the CDN; creating a DNS request result file comprising a plurality of domain name addresses and associated plurality of Internet Protocol, IP, addresses at which requested content of the CDN is accessible to a requesting device (104, 204); receiving, at a proxy server, a first DNS request intended for the DNS of the CDN, the first DNS request received from the requesting device and comprising a first domain name address for a requested content; and mitigating against an attack on the CDN comprising: determining whether the first domain name address of the first DNS request is included in the DNS request result file; when the first domain name address of the first DNS request is not included in the DNS request result file: providing, by the proxy server and to the requesting device (104, 204), an IP address comprising an embedded verification value, wherein the first IP address redirects the requesting device back to the proxy server; verifying that the requesting device (104, 204) is a legitimate requestor based on whether the proxy server receives a redirected request for the requested content from the requesting device that includes the embedded verification value; transmitting a redirect instruction to the requesting device (104, 204) that indicates an IP address associated with a hypertext transfer protocol, HTTP, server, wherein the redirect instruction further comprises a designated caching period instruction for the requesting device, the requesting device caching the IP address associated with the HTTP server for the designated caching period; and if a subsequent DNS request is received from the HTTP server, comparing the subsequent DNS request with the first DNS request; and if the subsequent DNS request matches the first DNS request, providing the subsequent DNS request to the DNS and saving a result from the DNS in the DNS request result file. providing, by the proxy server and to the requesting device (104, 204), an IP address comprising an embedded verification value, wherein the first IP address redirects the requesting device back to the proxy server; verifying that the requesting device (104, 204) is a legitimate requestor based on whether the proxy server receives a redirected request for the requested content from the requesting device that includes the embedded verification value; transmitting a redirect instruction to the requesting device (104, 204) that indicates an IP address associated with a hypertext transfer protocol, HTTP, server, wherein the redirect instruction further comprises a designated caching period instruction for the requesting device, the requesting device caching the IP address associated with the HTTP server for the designated caching period; and if a subsequent DNS request is received from the HTTP server, comparing the subsequent DNS request with the first DNS request; and if the subsequent DNS request matches the first DNS request, providing the subsequent DNS request to the DNS and saving a result from the DNS in the DNS request result file.