Dial-up is a form of network access in which a computer uses a modem to connect to a remote system over a telephone line. The modem converts computer data into signals that can travel through the phone network. Unlike a permanent broadband connection, dial-up typically connects only when a user or program places a call.
In cyber security, dial-up matters because it enabled remote access beyond local networks, expanding the number of systems that could be reached and the risks they faced. Attackers could search for systems accepting modem calls, while defenders needed to secure remote-access accounts, authentication, and connected computers. Its broader lesson remains relevant: making connectivity easier and more widespread can expand an organization’s attack surface unless security controls keep pace.