Yahoo has added more layers of security in its effort to shield people's online lives from government spying and other snooping.
The measures announced on Wednesday include the completion of a system that encrypts all information being transmitted from one Yahoo datacentre to another.
The technology is designed to make the emails and other digital information flowing through datacentres indecipherable to outsiders.
Search requests made from Yahoo's homepage are also now automatically encrypted, and the Sunnyvale, California, company is promising to make it more difficult for unauthorised intruders to hack into other services, including video chats, within the next few months. Yahoo strengthened the security of its email in January.
"Whether or not our users understand it, I feel it's our responsibility to keep them safe," Alex Stamos, Yahoo's recently hired chief information of security, told a small group of reporters.
Stamos, a former security consultant, joined Yahoo less than a month ago as part of the company's anti-snooping crusade.
Yahoo and other major technology companies, such as Google and Microsoft, have made online security a top priority during the last 10 months, amid a series of revelations about US government programs that have vacuumed up personal information about millions of web surfers in an effort to thwart terrorism.
The wide-ranging surveillance has been outlined in documents leaked to the media by former National Security Agency contractor Edward Snowden.
The technology industry's indignant response has been driven by financial self-interest as well as an aversion to government prying. Most internet services make money from ads that could be more difficult to sell if spying fears cause their audiences to shrink.
Yahoo, which has more than 800 million worldwide users, vowed late last year to encrypt its data centres by March 31 after reports that the US government had been secretly infiltrating the lines that transfer information overseas.