Yahoo said traffic moving between its data centers has been fully encrypted as of March 31. This comes several months after documents from Edward Snowden revealed the US government had penetrated the main communications links that connect Yahoo and Google's data centers.

Encrypting data links also kept with a previous promise by CEO Marissa Mayer to encrypt all information between its data centers by the end of March. Yahoo also said it had also turned on encryption for a range of other services.

Encryption of mail between its servers and other mail providers that support the SMTPLS standard was enabled in March. Yahoo, however, only turned on encryption by default between users and its email service this January.

Yahoo said its homepage and all search queries that run on it and most other Yahoo properties now also have HTTPS encryption enabled by default. If users, however, want an encrypted session for Yahoo News, Yahoo Sports, Yahoo Finance or Good Morning America on Yahoo, they must manually type "https" into the site's URL on their browsers.

Alex Stamos, chief information security officer at Yahoo, said the company had been working over the last several months to provide a more secure experience for its users. "Our broader mission is to not only make Yahoo secure, but improve the security of the overall web ecosystem," he said.

In 2012, the Electronic Frontier Foundation and other privacy activists called on CEO Marissa Mayer to enable HTTPS encryption for the company's communications services. Yahoo began offering HTTPS encryption for mail in 2012, but on an opt-in basis.

Over the years, Yahoo has faced pressure to encrypt more of its services. Highlighting the need for encryption was leaked information showing that GCHQ, Britain's surveillance agency, had captured webcam images from more than 1.8 million users of Yahoo Messenger. Yahoo said a new, encrypted version of Messenger will be released in the coming months.

Other companies like Google and Facebook have introduced more forms of encryption.