

The Terrorist Identities Datamart Environment, or TIDE, is a huge, classified database of people known to be terrorists, those who are suspected of having ties to terrorism, and in some cases those who are related to or are associates of known or suspected terrorists. It feeds to smaller lists that restrict people's abilities to travel on commercial airlines to or within the U.S.

The government does not need evidence that links someone to terrorism in order for the person to be included in the database. This is among the reasons the database and subsequent terror watch lists have been criticized by privacy advocates. Of the 1.1 million people in the database, 25,000 are U.S. citizens or legal permanent residents, the National Counterterrorism Center said.

The database's growth is a result of the government's response to a failed attempt to blow up a commercial airliner over Detroit on Christmas Day in 2009. The terror operative's name was included in the database before the attack, but it was not on a list that would have prevented him from getting on a U.S.-bound airplane. Since then, the government has lowered the standards for placing someone on the no-fly list and intelligence agencies have become more diligent about submitting names to the TIDE database.

The database was created after the 9/11 terror attacks when it became clear that the government's terror watch list was ineffective.

