Yahoo's fight against US surveillance disclosed

Yahoo said on Thursday that the US government had threatened to fine the company $250,000 a day if it didn't comply with demands to go along with an expansion of US surveillance by surrendering online information, a step the company regarded as unconstitutional.

The outlines of Yahoo's secret and ultimately unsuccessful court fight against government surveillance emerged when a federal judge ordered the unsealing of some material about Yahoo's court challenge.

In a statement, Yahoo said the government amended a law to demand user information from online services, prompting a challenge in 2007 during the George W. Bush administration.