The CAPPS II Data Mining System

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*The CAPPS II Data Mining System
The Transportation Security Administration has unveiled a new program known as the Computer System Passenger Prescreening System (CAPPS II), for the purpose of profiling and categorizing every airline passenger flying to, from or within the U.S. on the basis of a vaguely determined security threat level. Unfortunately, the rules for determining risk are not being revealed, and at least some of the information would come from secretive intelligence and law enforcement databases. Passengers would be unable to learn their own status, let alone learn what information it was based on and correct any errors.


  • The CAPPS II background check would consult government databases (including intelligence and law enforcement databases) to assign a risk assessment score (e.g. green, yellow, red) to each passenger. Higher scores would lead to heightened security procedures or complete grounding. [EPIC]

  • Passenger information would be checked against credit header information, banking history and other data held by various data aggregators - private corporations that maintain files on the commercial activities of most American citizens - in an effort to verify the traveler's identity. However, credit header information can be inaccurate and identity thieves could easily sidestep the identity check by presenting a false driver's license or passport, undercutting the system's entire mission. [EPIC]

  • According to a January Federal Register notice containing some details of the program, a yellow code in a person's file could be shared with other government agencies at the federal, state and local level, with intelligence agencies such as the CIA and with foreign governments and international agencies - all of which could use those designations for many purposes, including employment decisions and the granting of government benefits. [ACLU]

  • CAPPS II would not allow anyone to see the information that such a designation was based on, would not permit them a meaningful way to appeal, and would not reveal the criteria on which such judgments were based so they could avoid suspicion in the future. Individuals would not even have the right to confirm how they have been labeled. [ACLU]

  • On March 24, 2003, the Justice Department exempted the FBI's National Crime Information Center database, the country's most comprehensive law enforcement database, from a key section of the 1974 Privacy Act that guarantees that the database will be "accurate, relevant, timely, and complete." The system "is replete with inaccurate, untimely information," said Beryl Howell, former general counsel to the Senate Judiciary Committee. This is presumably the sort of database that would be consulted by CAPPS II. [AP]

  • MIT mathematicians have demonstrated that programs like CAPPS II are often ineffective at doing the job they are designed for. Random searches are generally more secure than profiling programs, allowing less potential terrorists to slip through. In addition, they show that even small error rates in a system like CAPPS II can lead to a huge number of innocents being mistakenly classified as threats. [MIT]

  • The Bush administration's 2005 fiscal budget request increases funding for CAPPS II from $45 million to $60 million. [FCW]

  • Sources:
    Electronic Privacy Information Center - Coalition Letter On Passenger Profiling [EPIC]
    American Civil Liberties Union - CAPPS II Will Invade Privacy [ACLU]
    New York Daily News - 13 Million On Terrorist Watch List [NYDN]
    Associated Press Justice Department Lifts FBI Database Limits [AP]
    Chakrabarti and Strauss - Carnival Booth [MIT]
    Federal Computer Week - CAPPS Gains in TSA Request [FCW]

    Further Info:
    Seattle Press - Opinion piece on CAPPS II - A call to boycott Delta until it discontinues its use of CAPPS II
    Internet News - A proposal for limited CAPPS II oversight
    American Civil Liberties Union - Information on the related ASSR database program

    Originally Written: 04-24-03
    Last Updated: 04-24-03

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