Lawful interception (LI) refers to the facilities in telecommunications and telephone networks that allow law enforcement agencies with court orders or other legal authorization to selectively wiretap individual subscribers. Most countries require licensed telecommunications operators to provide their networks with Legal Interception gateways and nodes for the interception of communications. The interfaces of these gateways have been standardized by telecommunication standardization organizations. As with many law enforcement tools, LI systems may be subverted for illicit purposes. With the legacy public switched telephone network (PSTN), wireless, and cable systems, lawful interception (LI) was generally performed by accessing the mechanical or digital switches supporting the targets' calls. The introduction of packet-switched networks, softswitch technology, and server-based applications during the past two decades fundamentally altered how LI is undertaken. Lawful interception differs from the dragnet-type mass surveillance sometimes done by intelligence agencies, where all data passing a fiber-optic splice or other collection point is extracted for storage or filtering. It is also separate from the data retention of metadata that has become a legal requirement in some jurisdictions.
Terminology
Lawful interception is obtaining communications network data pursuant to lawful authority for the purpose of analysis or evidence. Such data generally consist of signaling or network management information or, in fewer instances, the content of the communications. If the data are not obtained in real-time, the activity is referred to as access to retained data (RD). There are many bases for this activity that include infrastructure protection and cybersecurity. In general, the operator of public network infrastructure can undertake LI activities for those purposes. Operators of private network infrastructures in the United States have an inherent right to maintain LI capabilities within their own networks unless otherwise prohibited. One of the bases for LI is the interception of telecommunications by law enforcement agencies (LEAs), regulatory or administrative agencies, and intelligence services, in accordance with local law. Under some legal systems, implementations—particularly real-time access to content—may require due process and receiving proper authorization from competent authorities—an activity that was formerly known as "wiretapping" and has existed since the inception of electronic communications. The material below primarily treats this narrow segment of LI.
Technical description Almost all countries have lawful interception capability requirements and have implemented them using global LI requirements and standards developed by the European Telecommunications Standards Institute (ETSI), Third Generation Partnership Project (3GPP), or CableLabs organizations—for wireline/Internet, wireless, and cable systems, respectively. In the USA, the comparable requirements are enabled by the Communications Assistance for Law Enforcement Act (CALEA), with the specific capabilities promulgated jointly by the Federal Communications Commission and the Department of Justice. In the USA, lawful intercept technology is currently patented by a company named Voip-pal.com under the USPTO Publication #: 20100150138. Governments require phone service providers to install a legal interception gateway (LIG), along legal interception nodes (LIN), which allow them to intercept in real-time the phone calls, SMS messages, emails and some file transfers or instant messages. These LI measures for governmental surveillance have been in place since the beginning of digital telephony. To prevent investigations' being compromised, LI systems may be designed in a manner that hides the interception from the telecommunications operator concerned. This is a requirement in some jurisdictions. Alternatively, LI systems may be designed using technology such as transparent decryption, which ensures that access or interception is necessarily overt in order to disincentivize abuse of authority. To ensure systematic procedures for carrying out interception, while also lowering the costs of interception solutions, industry groups and government agencies worldwide have attempted to standardize the technical processes behind lawful interception. One organization, ETSI, has been a major driver in lawful interception standards not only for Europe, but worldwide. This architecture attempts to define a systematic and extensible means by which network operators and law enforcement agents (LEAs) can interact, especially as networks grow in sophistication and scope of services. Note this architecture applies to not only “traditional” wireline and wireless voice calls, but to IP-based services such as voice over IP, email, instant messaging, etc. The architecture is now applied worldwide (in some cases with slight variations in terminology), including in the United States in the context of CALEA conformance. Three stages are called for in the architecture:
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