The attacks on the Brussels airport and metro system are evidence that terrorist groups like ISIS are returning to tried-and-true methods – micro-attacks with macro-effect. And they highlight an immediate need to rethink U.S. airport security strategies by local law enforcement and the Department of Homeland Security.

Recall the 2008 terrorist attacks in Mumbai, a series of 12 shootings and bombings carried out by the Pakistani terrorist organization Lashkar-e-Taiba. The attacks left nearly 200 dead and injured more than 300.