1 definition by Internet Veteran
The shady underground world of the Internet where most seriously illegal activities are conducted. The Undernet is the "underground of the Internet".
Phishers steal identification data from unsuspecting people and then sell that data on the Undernet, which among other things contains this huge black market operating under the Internet where all kinds of ill-gotten data are bought and sold. The seeds for identity theft are sown on the Undernet.
by Internet Veteran April 26, 2012