FILE - In this Wednesday, Oct. 17, 2012, photo, shows a sign in front of Yahoo! headquarters in Sunnyvale, Calif. Yahoo said Monday, Nov. 18, 2013, that it is expanding its efforts to protect its users' online activities from prying eyes by encrypting all the communications and other information flowing into the Internet company's data centers around the world. SAN FRANCISCO (AP) - Yahoo is expanding its efforts to protect its users' online activities from prying eyes by encrypting all the communications and other information flowing into the Internet company's data centers around the world. The commitment announced Monday by Yahoo Inc. CEO Marissa Mayer follows a recent Washington Post report that the National Security Agency has been hacking into the communications lines of the data centers run by Yahoo and Google Inc. to intercept information about what people do and say online. Yahoo had previously promised to encrypt its email service by early January. Now, the Sunnyvale, Calif., company plans to have all data encrypted by the end of March to make it more difficult for unauthorized parties to decipher the information. Google began to encrypt its Gmail service in 2010 and has since introduced the security measure on many other services. The Mountain View, Calif., company has promised to encrypt the links to its data centers, too. A Google engineer said that task had been completed in a post on his Google Plus account earlier this month, but the company hasn't yet confirmed all the encryption work is done. Other documents leaked to various media outlets by former NSA contractor Edward Snowden this year have revealed that Yahoo, Google and several other prominent technology companies, including Microsoft Corp., Facebook Inc. and Apple Inc., have been feeding the U.S. government some information about their international users under a court-monitored program called PRISM. The companies maintain they have only surrendered data about a very small number of users, and have only cooperated when legally required. The NSA says its online surveillance programs have played an instrumental role in thwarting terrorism. The increased use of encryption technology is aimed at stymieing government surveillance that may be occurring without the companies' knowledge. Even when it's encrypted, online data can still be heisted, but the information looks like gibberish without the decoding keys. "I want to reiterate what we have said in the past: Yahoo has never given access to our data centers to the NSA or to any other government agency," Yahoo CEO Marissa Mayer wrote in a Monday post on the company's Tumblr blog. Facebook also has said it's cloaking its social networking network with greater encryption, but hasn't publicly set a timetable for getting all the added protection in place. Debunking the perception that the NSA and other U.S. government agencies can easily vacuum up potentially sensitive information about people's online lives is important to Yahoo, Google and other Internet companies because they need Web surfers to regularly use their services so they can sell more of the digital ads that bring in most of their revenue. The companies fear the government spying revelations eventually will drive some people away from their services and make it more difficult to attract more users outside the U.S. If that were to happen, it could slow the companies' financial growth and undercut their stock prices. Yahoo has been struggling to boost its revenue for years, making it even more important for the company to reassure its 800 million users worldwide about the sanctity of their personal information.