Telephone companies and mobile service providers maintain records of communication activity. These records typically contain information such as the date, time, and duration of calls, as well as the phone numbers involved. Whether these records include the content of SMS or multimedia messages (MMS) is variable. For example, a billing statement might show that a text message was sent or received at a particular time to a specific number, but it will usually not display the messages text.
The preservation and availability of communication metadata are important for legal and investigative purposes. Law enforcement agencies, with proper legal authorization, can use this data to establish patterns of communication, identify potential witnesses, or build timelines of events. Historically, access to call detail records has been a standard investigative tool; however, the increasing prevalence of encrypted messaging apps and data privacy regulations have changed the landscape of electronic surveillance.