Anonymity networks

Tor is a free overlay network for enabling anonymous communication. Built on free and open-source software and more than seven thousand volunteer-operated relays worldwide, users can have their Internet traffic routed via a random path through the network.

Public-key cryptography, or asymmetric cryptography, is the field of cryptographic systems that use pairs of related keys. Each key pair consists of a public key and a corresponding private key. Key pairs are generated with cryptographic algorithms based on mathematical problems termed one-way functions. Security of public-key cryptography depends on keeping the private key secret; the public key can be openly distributed without compromising security. There are many kinds of public-key cryptosystems, with different security goals, including digital signature, Diffie-Hellman key exchange, public-key key encapsulation, and public-key encryption.

Ennetcom was a Netherlands based communications network and service provider.

Sky Global was a communications network and service provider founded in 2008 in Vancouver, Canada. It developed the world's largest encrypted messaging network called Sky ECC, operating through three servers of the OVHcloud company in Roubaix, France. A significant share of the system's users were international crime organizations involved in drug trafficking, and the company management was suspected of collusion.

EncroChat was a Europe-based communications network and service provider that offered modified smartphones allowing encrypted communication among subscribers. It was used primarily by organized crime members to plan criminal activities. Police infiltrated the network between at least March and June 2020 during a Europe-wide investigation. An unidentified source associated with EncroChat announced on the night of 12–13 June 2020 that the company would cease operations because of the police operation.

ZeroTier, Inc. is a software company with a freemium business model based in Irvine, California. ZeroTier provides proprietary software, SDKs and commercial products and services to create and manage virtual software-defined networks. The company's flagship end-user product ZeroTier One is a client application that enables devices such as PCs, phones, servers and embedded devices to securely connect to peer-to-peer virtual networks.

Operation Trojan Shield (stylized TRØJAN SHIELD), part of Operation Ironside, was a collaboration by law enforcement agencies from several countries, running between 2018 and 2021. It was a sting operation that intercepted millions of messages sent through the supposedly secure smartphone-based proprietary messaging app ANOM (also stylized as AN0M or ΛNØM). The ANOM service was widely used by criminals, but instead of providing secure communication, it was actually a trojan horse covertly distributed by the United States Federal Bureau of Investigation (FBI) and the Australian Federal Police (AFP), enabling them to monitor all communications. Through collaboration with other law enforcement agencies worldwide, the operation resulted in the arrest of over 800 suspects allegedly involved in criminal activity in 16 countries. Among the arrested people were alleged members of Australian-based Italian mafia, Albanian organised crime, outlaw motorcycle clubs, drug syndicates and other organised crime groups.

Tor Mail was a Tor hidden service that went offline in August 2013 after an FBI raid on Freedom Hosting. The service allowed users to send and receive email anonymously to email addresses inside and outside the Tor network.