http://ttevhjjsjxz6uqqcjkbig5cycd7n7xv7cmd6f5fcvrqaaa7f3bj36wad.onion/technology/security/pow/index.html
This computation consumes processing
time, memory, storage and energy in the server, opening the door to a
vulnerability known as Denial of Service (DoS), where an attacker spawns
multiple connection attempts in order to overload the service and render it
inaccessible.