BOSTON - If the National Security Agency is indeed amassing a colossal database of Americans' phone records, one way to use all that information is in "social network analysis," a data-mining method that aims to expose previously invisible connections among people.

Social network analysis has gained prominence in business and intelligence circles under the belief that it can yield extraordinary insights, such as the fact that people in disparate organizations have common acquaintances. Companies can buy social networking software to help determine who has the best connections for a particular sales pitch.

So it did not surprise many security analysts to learn Thursday from USA Today that the NSA is applying the technology to billions of phone records.

"Who you're talking to often matters much more than what you're saying," said Bruce Schneier, a security expert.

To be sure, monitoring newer communications services is probably harder than getting billing records from landline phones. USA Today reported that the NSA has collected call logs from the three largest U.S. phone companies, BellSouth Corp., AT&T Inc. and Verizon Communications Inc.

That level of cooperation confirmed the fears of many privacy analysts, who pointed out that AT&T is already being sued in federal court in San Francisco for allegedly giving the NSA access to contents of its phone and Internet networks.

WHAT ABOUT CELLS?

It remains unclear whether other communications providers have been asked for call logs.

Verizon Wireless spokesman Jeffrey Nelson definitively said his company was "not involved in this situation." His counterparts at Cingular and Sprint Nextel Corp. were less explicit and did not deny any participation.

In an e-mail statement to The Associated Press, T-Mobile USA Inc. said it does not participate "in any NSA program for warrant-less surveillance and acquisition of call records, and T-Mobile has not provided any such access to communications or customer records."

Even without cell phone carriers' help, of course, calls between wireless subscribers and Verizon, AT&T and BellSouth landlines presumably would be captured.

WHAT ABOUT THE WEB?

Representatives for AOL LLC said the company complies with individual government subpoenas and court orders but does not have a blanket program for broader sharing of customer data. Microsoft Corp. had "never engaged in the type of activity referenced in these articles," according to a statement. Google Inc. spokesman Steve Langdon said his company does not participate, either.

Yahoo Inc. officials say they comply with subpoenas, but refused to elaborate.

WHAT ABOUT VOIPs?

Even Skype, the popular Internet phone service that encrypts its calls -- which presumably prevents monitoring of their content -- is thought to be vulnerable to who's-calling-whom traffic analysis.

Other tiny, free voice-over-Internet services likely don't bother to maintain the kinds of call logs that Verizon, BellSouth and AT&T apparently handed over, said Jeff Pulver, an authority on the technology.

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