A majority of Internet traffic and online data lives beneath the surface of the Web as we know it. In the darkest, hidden recesses of the Internet, individuals engage in illicit activities and cybercrimes, but also in substantial activism, journalism and sensitive communications. Hackers operate anonymously and in great numbers in this environment. In various secretive forums, they discuss techniques, software vulnerabilities and exploits, and tools of the trade. Hackers and other bad actors also offer their services for hire, and operate marketplaces that sell software vulnerabilities, hacking tools, corporate trade secrets, and stolen financial, health care and other sensitive personal information. This environment is also used to host command-and-control servers that direct denial of service (DoS) botnet attacks and communicate with malware residing in corporate networks.