Study finds hackers and military sites lurking in the Internet's phantom zones:

Broadband customers and U.S. military systems are the most common victims of an online phenomenon researchers have dubbed "dark address space," which leaves some 100 million hosts completely unreachable from portions of the Internet.

For a variety of reasons ranging from contract disputes among network operators to simple router misconfiguration, over five percent of the Internet's routable address space lacks global connectivity, according to the results of a three-year study by researchers at Massachusetts-based Arbor Networks, to be released Tuesday.

"Popular belief holds that the Internet represents a completely connected graph," says Craig Labovitz, Arbor Networks' director of network architecture. "It turns out that's just not true."