As he has with other networks, Lamo found the keys to WorldCom’s kingdom in open Internet proxy servers. In normal operation, a proxy server is a dedicated machine that sits between a local network and the outside world, passing internal surfers’ Web requests out to the Internet, often caching the results to speed up subsequent visits to the same URL.
But it’s easy and common for administrators to inadvertently misconfigure proxy servers, allowing anyone on the Internet to channel through them. Sometimes companies and organizations even unknowingly run proxies. Hackers and privacy-conscious netizens catalog these open proxies, using them to anonymize their surfing. Lamo has perfected a different use: jumping through them to pose as a node on a company’s internal network.