Earlier this week Reuters news agency reported that Yahoo developed a bespoke piece of software to scan emails relevant to hundreds of millions of Yahoo Mail accounts in search of specific information that intelligence officials at the National Security Agency (NSA) and FBI sought access to.
Reuters reported at the time that its sources, including three former Yahoo employees, were only aware that the intelligence officials were looking "to search for a set of characters", which the sources said could mean "a phrase in an email or an attachment".
Yahoo originally issued a short statement in which it said it was "a law abiding company" and compliant with US laws. However, it has subsequently issued another statement in which it said the Reuters article is "misleading".
The company said: "We narrowly interpret every government request for user data to minimise disclosure. The mail scanning described in the article does not exist on our systems."
According to Yahoo's transparency report, which includes details of the requests it receives from government agencies for data it holds and its response to those requests, the number of Yahoo accounts impacted by requests by US authorities for access to data was in the tens of thousands. However, the figures published did not include the number of requests made by US authorities under the Foreign Intelligence Surveillance Act (FISA) or the number of accounts impacted by those requests during the second half of 2015.
Yahoo said in its report: "With the passage of the USA Freedom Act in May 2015, US law now clearly allows companies like Yahoo to disclose additional information about FISA requests. The additional detail that Yahoo can now disclose is subject to a six-month reporting delay. Accordingly, we will provide the data for the most recent reporting period when we update our report in six months."
Yahoo's transparency report covering the first six months in 2016 has not yet been published.
The BBC reported that Ireland's data protection authority has asked Yahoo for more details of the activities it reportedly engaged in.
"Any form of mass surveillance infringing on the fundamental privacy rights of EU citizens would be viewed as a matter of considerable concern," the Irish authority said, according to the BBC.
