The company complied with a classified US government demand, scanning hundreds of millions of Yahoo Mail accounts at the behest of the National Security Agency or FBI, said three former employees and a fourth person apprised of the events.
Some surveillance experts said this represents the first case to surface of a US internet company agreeing to an intelligence agencys request by searching all arriving messages, as opposed to examining stored messages or scanning a small number of accounts in real time.
It is not known what information intelligence officials were looking for, only that they wanted Yahoo to search for a set of characters. That could mean a phrase in an email or an attachment, said the sources, who did not want to be identified.
The request to search Yahoo Mail accounts came in the form of a classified edict sent to the companys legal team, according to the three people familiar with the matter.
US phone and internet companies are known to have handed over bulk customer data to intelligence agencies. But some former government officials and private surveillance experts said they had not previously seen either such a broad demand for real-time web collection or one that required the creation of a new computer program.
Experts said it was likely that the NSA or FBI had approached other internet companies with the same demand, since they evidently did not know what email accounts were being used by the target. The NSA usually makes requests for domestic surveillance through the FBI, so it is hard to know which agency is seeking the information.
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