Here's the latest revelation from the Guardian's NSA documents. All your internet data are belong to us!

The National Security Agency is storing the online metadata of millions of internet users for up to a year, regardless of whether or not they are persons of interest to the agency, top secret documents reveal.

Metadata provides a record of almost anything a user does online, from browsing history – such as map searches and websites visited – to account details, email activity, and even some account passwords. This can be used to build a detailed picture of an individual's life.

The Obama administration has repeatedly stated that the NSA keeps only the content of messages and communications of people it is intentionally targeting – but internal documents reveal the agency retains vast amounts of metadata.

An introductory guide to digital network intelligence for NSA field agents, included in documents disclosed by former contractor Edward Snowden, describes the agency's metadata repository, codenamed Marina. Any computer metadata picked up by NSA collection systems is routed to the Marina database, the guide explains. Phone metadata is sent to a separate system.

"The Marina metadata application tracks a user's browser experience, gathers contact information/content and develops summaries of target," the analysts' guide explains. "This tool offers the ability to export the data in a variety of formats, as well as create various charts to assist in pattern-of-life development."

The guide goes on to explain Marina's unique capability: "Of the more distinguishing features, Marina has the ability to look back on the last 365 days' worth of DNI metadata seen by the Sigint collection system, regardless whether or not it was tasked for collection." [Emphasis in original.]

On Saturday, the New York Times reported that the NSA was using its metadata troves to build profiles of US citizens' social connections, associations and in some cases location, augmenting the material the agency collects with additional information bought in from the commercial sector, which is is not subject to the same legal restrictions as other data.

The ability to look back on a full year's history for any individual whose data was collected – either deliberately or incidentally – offers the NSA the potential to find information on people who have later become targets. But it relies on storing the personal data of large numbers of internet users who are not, and never will be, of interest to the US intelligence community.

Marina aggregates NSA metadata from an array of sources, some targeted, others on a large scale. Programs such as Prism – which operates through legally compelled "partnerships" with major internet companies – allow the NSA to obtain content and metadata on thousands of targets without individual warrants.