“Hackers of old used wardialing to explore the telephone network much like port-scanning is used today to explore the Internet.”
He dialed 56,874 Finnish toll-free numbers over 40 days and recorded the first minute of each. Two percent picked up with something interesting, and there were only 74 unique answers among them. The phone network is a century of systems nobody has documented or switched off. Somebody is still paying for every one of those lines.