Most administrators feel their dial-up servers are secure since no one outside the company knows their phone numbers. That is where information gathering and wardialers come in.

  • Hackers find the voice numbers to the company. Chances are the dial-up numbers start with the same prefixes.
  • Some companies even put voice numbers on their Web page.
  • Hackers can also get numbers from phone books or other information sources.
  • Hackers can check the name and number registered with the InterNIC.
  • The number listed is probably the Network Operations Center (NOC), and is often where the modems are usually located.