Twitter Inc said it has implemented a security technology that makes it harder to spy on its users and called on other Internet firms to do the same, as Web providers look to thwart spying by government intelligence agencies. The online messaging service, which began scrambling communications in 2011 using traditional HTTPS encryption, said on Friday it has added an advanced layer of protection for HTTPS known as forward secrecy. A year and a half ago, Twitter was first served completely over HTTPS, the company said in a blog posting. Since then, it has become clearer and clearer how important that step was to protecting our users privacy. Twitters move is the latest response from U.S. Internet firms following disclosures by former spy agency contractor Edward Snowden about widespread, classified U.S. government surveillance programs. Facebook Inc, Google Inc, Microsoft Corp and Yahoo Inc have publicly complained that the government does not let them disclose data collection efforts.