Beacon is a Cobalt Strike payload for long-term command and control of compromised hosts. It works like other Metasploit Framework payloads. You may embed it into an executable, add it to a document, or deliver it with a client-side exploit. Beacon downloads tasks using HTTP requests. For extra stealth, Beacon may use DNS requests to check if a task is available. This limits the communications between the penetration tester and the target network. You may configure Beacon to connect to multiple domains (who cares if that first one is blocked)
Source: https://thehackernews.com/2012/10/beacon-new-advance-payload-for-cobalt.html