A simple but effective resource to get students to play the role of a server unable to cope with too many requests at the same time. A series of simple, single digit addition sums will appear on the screen and the student(s) participating simply have to shout out the answers. The slide automatically changes after 7 seconds and the number of sums (requests) increases each time - by the time they get to slide 10 they should have been unable to cope with the number of requests, as a server would with a DDoS attack.