US law-enforcement agents are being taught to make use of social-networking sites such as Facebook to befriend suspects and gather proof, according to documents issued by advocacy group The Electronic Frontier Foundation (EFF).

The Justice Department internal training document, called Obtaining and Using Evidence from Social Networking Sites, disclosed that spies for the federal bureau of investigation (FBI) and other agencies make fake profiles on sites including My Space and Facebook to try to arrest suspects by getting access to their social networks.

The training handbook stated that such operations can be practicable to talk with suspects or targets, expose their private communications, gain access to non-public data and map social relations and networks. Information gleaned can also be utilized confirm alibis and set up locations, the 33-page document disclosed.

Social networking sites are also a good source of information on defense witnesses, the Justice Department's slide presentation said.

"Knowledge is power," the document said. "Research all witnesses on social-networking sites."

The written document notes the potential troubles with such secret operations with the words, "If agents violate terms of service, is that 'otherwise illegal activity?'" referring to site policies against establishing accounts with a false identity.

While the Justice Dept document left the query open, a written document released to EFF by the tax-collecting Internal Revenue Service mentioned that IRS workers are banned from using deception or false online accounts to get data about taxpayers.

The EFF, which advocates for online confidentiality rights, suspended statement on the Justice Department documents but did praise the IRS plan. (With Input from Agencies)