Think your Skype messages get end-to-end encryption? Think again – ARS TECHNICA
Ars catches Microsoft accessing links we sent in our test messages.
Still, there’s a widely held belief—even among security professionals, journalists, and human rights activists—that Skype somehow offers end-to-end encryption, meaning communications are encrypted by one user, transmitted over the wire, and then decrypted only when they reach the other party and are fully under that party’s control. This is clearly not the case if Microsoft has the ability to read URLs transmitted back and forth.
“The problem right now is that there’s a mismatch between the privacy people expect and what Microsoft is actually delivering,” Matt Green, a professor specializing in encryption at Johns Hopkins University, told Ars. “Even if Microsoft is only scanning links for ‘good’ purposes, say detecting malicious URLs, this indicates that they can intercept some of your text messages. And that means they could potentially intercept a lot more of them.”
Specifics of the Microsoft scanning remain unclear; one possibility is that the scanning and spam-checking happen on Microsoft servers as communications pass through supernodes. Another possibility is that the Skype client on each end-user machine uses “regular expression” programming techniques built into the software and sends only the links to Microsoft servers.
“Either way, the finding does confirm that somewhere along the stream, Microsoft/Skype has the ability to intercept/extract content from your communications though we can’t conclusively say where,” Soltani wrote in an e-mail to Ars. “For example, even if the scanning was happening client side, it’s plausible that MS could be compelled to push a ruleset to the Skype client that just logs/transmits all our activity (similar to what CarrierIQ was doing on the HTC phones).”
To be fair, Microsoft’s scanning of Skype messages isn’t too different from techniques Facebook reportedly employs, and what any number of other online services do, too. As Green notes, these companies have a duty to make sure their services aren’t abused to circulate malware.
What’s different in the case of Skype is the misunderstanding among many users that links and other content sent over the service are private. This misunderstanding is all the more unfortunate given the possibility that this information plucked out of private messages could be logged and retained for as long as some nameless, faceless Microsoft manager deems appropriate. Add to that the fact that a server bearing a Microsoft IP address very well may click on any link you send over Skype and it may not be such a good option for dissidents trying to lay low.