SAN FRANCISCO • The U.S. government is seeking software that can mine social media to predict everything from terrorist attacks to foreign uprisings, according to requests posted online by federal law enforcement and intelligence agencies.

Hundreds of intelligence analysts already sift overseas Twitter and Facebook posts to track events such as the Arab Spring. But in a formal "request for information" from potential contractors, the FBI recently outlined its desire for a digital tool to scan the entire universe of social media — more data than humans could ever crunch.

The Department of Defense and the Office of the Director of National Intelligence also have solicited the private sector for ways to automate the process of identifying emerging threats and upheavals using the billions of posts people around the world share every day.

"Social media has emerged to be the first instance of communication about a crisis, trumping traditional first responders that included police, firefighters, EMT, and journalists," the FBI wrote in its request. "Social media is rivaling 911 services in crisis response and reporting."

The proposals already have raised privacy concerns among advocates who worry that such monitoring efforts could have a chilling effect on users. Ginger McCall, director of the open government project at the Washington-based Electronic Privacy Information Center, said the FBI has no business monitoring legitimate free speech without a narrow, targeted law enforcement purpose.

"Any time that you have to worry about the federal government following you around peering over your shoulder listening to what you're saying, it's going to affect the way you speak and the way that you act," McCall said.

The FBI said in a statement to The Associated Press that their proposed system is only meant to monitor publicly available information and would not focus on specific individuals or groups but on words related to criminal activity.

Analyzing public information is nothing new in the world of intelligence. During the Cold War, CIA operatives read Russian newspapers and intercepted television and radio broadcasts in hopes of inferring what Soviet leaders were thinking.

But the rise of social media over the last few years has dramatically changed both the kinds and amount of freely available information. For example, Twitter CEO Dick Costolo said at a recent conference that users of the micro-blogging service send out an average of 1 billion tweets every three days.