Yahoo announced a number of encryption enhancements to its email and other online services, and also announced it was finally encrypting communication links between its data centers. The company was criticized heavily for its lack of encryption on its services, which experts said facilitated the NSA s ability to snoop on traffic, and harmed users ability to keep their identities and personal information secure from criminals operating on the web. Yahoo was one of the last major web-based email providers to turn on SSL by default, doing so in January.
Source: https://threatpost.com/yahoo-encrypts-data-center-links-boosts-other-services/105228/