So let's say a company is spending a huge amount of money to eradicate unauthorized dial-in modems. This little-known but widespread threat is the focus of this article. Many companies with dozens of employees still get by with a 56KB modem as their sole access to the Internet. Even major companies often connect a small branch office with nothing more than an ISDN or DSL modem. While these will not answer incoming calls, they can pose other threats.
Serious crackers pay special attention to fax lines.
All too often, when 5 p.m. rolls around, a fax line will serve as an unauthorized dial-in modem. External Attacks Against Modems Even though your modem scanner may show that none of your modems will answer incoming calls, some can be forced to hang up and redial another number while running a PPP session. This has been exploited by pornography scams. An attacker Web site sends Java code to hang up the porn surfer's modem. It then forces it to redial a long distance number in a country that has some sort of 900 service.