In a blockbuster scoop, Reuters’ Joseph Menn is reporting that Yahoo secretly built a software program in 2015 that scanned all its millions of customers’ incoming emails at the behest of US intelligence officials, which led to its chief security officer resigning in protest.

Yahoo secretly monitored emails on behalf of the US government – report Read more

We don’t know exactly what the US government might have been searching for, but we do know that this is potentially a huge privacy violation that strikes at the heart of the fourth amendment’s prohibition on indiscriminate search and seizure. Yahoo’s reported secret collaboration with the US government also brings up several points that warrant further investigation. (“Yahoo is a law abiding company, and complies with the laws of the United States,” the company said in a statement to Reuters.)

Much of the discussion about Edward Snowden’s 2013 revelations has focused on the NSA’s mass phone spying program that the courts later ruled illegal. But many people forget that the New York Times also reported, in 2013, based on previously published Snowden documents, that the NSA had been scanning countless emails going into and out of the US for years, looking for certain keywords.

This Yahoo story seems to be an escalation of this type of “about” or “upstream” surveillance, which was once done by the NSA by secretly wiretapping internet cables owned by AT&T and others. Since many email companies have started encrypting their emails in transit since that story came out, the NSA probably can’t do that type of surveillance unilaterally (or with the help of AT&T) anymore. The US government now seems to be moving to force internet companies to do this type of mass surveillance for them, on the companies’ servers, where the data remains accessible.

Civil liberties groups have been calling this type of “about” mass surveillance – in which the government scans all emails for certain keywords – illegal and unconstitutional for years. But so far, no court has ruled definitively one way or another (mainly because the US has been hiding behind official secrecy to prevent it).

Now the question reporters should be asking is: if Yahoo received this secret order, what about the other tech giants? Did Google, Facebook and Microsoft receive similar demands to wiretap their own systems for searching all emails at the behest of the US government or others?

The Yahoo story, if borne out, would be the quintessential example of how government-mandated backdoors are dangerous for everyone’s security, and why end-to-end encryption needs to be standard on all our communications platforms.

Incredibly, Yahoo apparently built this backdoor into its email system without even telling its then security chief, Alex Stamos. “The sources said the program was discovered by Yahoo’s security team in May 2015, within weeks of its installation,” Menn reported. “The security team initially thought hackers had broken in.”

Stamos was reportedly furious and resigned in protest. “Due to a programming flaw [in the software], he told [Yahoo executives] hackers could have accessed the stored emails,” Menn explained. Security experts have been highlighting for years how backdoors not only give access to the “good guys” but also could let other criminals or foreign governments into our communications systems.

This is exactly the type of mass surveillance that end-to-end encryption would prevent. Currently, Yahoo emails are encrypted as they travel from one server to another, but can be read by Yahoo at the company’s discretion.

Stamos is now the director of security at Facebook, which coincidentally just rolled out end-to-end encryption on its popular Facebook Messenger app, which is used by more than 900 million people around the world. Unfortunately, much like Google’s just launched (and much maligned) new chat program Allo, Facebook Messenger’s end-to-end encryption is opt-in, and so only a tiny fraction of users are likely to turn it on.

This type of encryption should be standard and turned on by default in all messaging apps (and ideally email as well). Users should consider switching to apps where default end-to-end encryption is already turned on, including WhatsApp, Signal and Apple’s iMessage.

Finally, Yahoo’s possible betrayal of its users is another example of why whistleblowers and leaks to the press are so important. The US government considers this type of surveillance “legal” even though it shocks the conscience of many ordinary Americans and dozens of civil liberties groups have been attempting to have courts rule it illegal for years. The only reason we know about it is because brave people came forward at the risk of their freedom to tell us. For that, we owe them a great debt.