TSA tester has been probing airport weaknesses for five years. Screeners who fail to detect contraband are “pulled off the line” and retrained before being allowed back. Every TSA X-ray machine has a Threat Image Projection system, which digitally inserts images of guns, knives and bombs into the X-rays of luggage. Some 69,929 threat image tests are conducted on an average day, or more than 25 million tests per year. An array of other tests also are conducted to assess screeners, including the red team ones.”]
Source: https://taosecurity.blogspot.com/2008/01/tsa-lessons-for-security-analysts.html