On October 11, the FBI issued an alert warning of possible terrorist attacks on American soil or against U.S. international interests.

CNN: Americans urged to carry on despite terror alert

When he returned, media reports say the FBI questioned him after a warning from a foreign intelligence service (presumably Russia's).

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Canadian Solicitor General Lawrence MacAulay said Tuesday that information from the Canadian Security Intelligence Service was shared with the FBI and led to the Ashcroft warning.

CNN: Information from Canada helped lead to alert, official says

Critics painted the FBI agents as inexperienced locals, saying that reading the Miranda warning ensures non-cooperation and arguing that a more "suitable" entity than the FBI should have been in charge.

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The FBI is using the case as a warning to Internet users everywhere not to send nude photos of themselves electronically.

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The FBI is seeking to develop an early-warning system based on material "scraped" from social networks.

BBC: FBI plans social network map alert mash-up application

On Monday, FBI Director Robert Mueller insisted the agency had "no warning signs" of last week's attacks.

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In July and August, the FBI's National Infrastructure Protection Center took the rare step of warning people around the world about the impending threat of the "Code Red" worm -- named after the soft drink favored by the security team that first analyzed it.

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It's serious enough, he said, that the FBI issued an alert about it to the U.S. Space Command, giving U.S. forces warning that the action on the cyber front could affect them, too.

CNN: U.S. Army kick-starts cyberwar machine