Telecommunications data retention

In the field of telecommunications, data retention (or data preservation) generally refers to the storage of call detail records (CDRs) of telephony and internet traffic and transaction data () by governments and commercial organisations. In the case of government data retention, the data that is stored is usually of telephone calls made and received, emails sent and received, and websites visited. Location data is also collected.

The primary objective in government data retention is traffic analysis and mass surveillance. By analysing the retained data, governments can identify the locations of individuals, an individual's associates and the members of a group such as political opponents. These activities may or may not be lawful, depending on the constitutions and laws of each country. In many jurisdictions access to these databases may be made by a government with little or no judicial oversight (e.g., United States, UK, Australia).

In the case of commercial data retention, the data retained will usually be on transactions and web sites visited.

Data retention also covers data collected by other means (e.g., by automatic numberplate recognition systems) and held by government and commercial organisations.

In 2015, the Australian government introduced mandatory data retention laws that allows data to be retained up to two years. The scheme is estimated to cost at least AU$400 million per year to implement, working out to at least $16 per user per year. It will require telecommunication providers and ISPs to retain telephony, Internet and email metadata for two years, accessible without a warrant, and could possibly be used to target file sharing. The Attorney-General has broad discretion on which agencies are allowed to access metadata, including private agencies.

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