Dark internet

The term dark internet, dark web or dark address refers to any or all of the unreachable network hosts on the Internet. It should not be confused with "deep web" or "darknet" which refer to dynamic content sites and illegal file sharing networks, respectively.
The most common cause of dark address space is router misconfiguration. Some military sites on the archaic MILNET address blocks also frequently fall into dark addresses. It is also speculated that hackers utilize malicious techniques to hijack private routers to either divert traffic or mask illegal activity.
The dark internet received a lot of attention in 2001 when many security organizations, including Arbor Networks, identified rogue dark networks as a potential farm for denial-of-service attacks and other illegal activity.