Special attention should continue to be directed for unattended packages, suspicious persons and vehicles. IEDs concealed as unattended baggage remains a staple tactic of terrorist adversaries targeting mass transit. Noteworthy examples are the attacks in Madrid, March 2004, and in London, July 2005. While some placed IEDs used in these and other attacks were hidden, others remained in plain sight as unattended baggage.
(U//LES) Violent extremists have used explosives made from ingredients readily available at retail stores in the United States or over the Internet. Triacetone triperoxide (TATP) and hexamethylene triperoxide diamine (HMTD) are two common homemade explosives built with hydrogen peroxide.