Full body scanning machines- dubbed "virtual strip searches" by critics, that existed at various airports since the beginning of 2010, will soon be find their way to trains, subways and boats.
The Department of Homeland Security says the body scans and pat-downs are necessary to keep people safe.
"It's all about security," Janet Napolitano, the Homeland Security Secretary, said.
"It's all about everyone recognising their role. Terrorists are going to continue to probe the system and try to find a way through," Napolitano said in a media interview.
She said as aviation security tightens, "we have to also be thinking now about going on to mass transit or to trains or maritime".
Her comments were a response to a question about what terrorists would be thinking in the future.
She didn't elaborate on what enhanced security at train stations might look like, however trains have already been terrorist targets in England, Russia and Spain, with catastrophic results; just last month, a Pakistani-American was arrested after a thwarted plot to bomb the Washington, DC metro system.
So it's somewhat surprising the government took this long to acknowledge our other modes of transport are also at risk.
"I think the tighter we get on aviation, we have to also be thinking now about going on to mass transit or to trains or maritime," she said.
"So what do we need to be doing to strengthen our protections there?" Napolitano's comments came as outrage grows over what some call intrusive X-ray scans and pat-downs that the Transportation Security Administration has used to screen airline passengers.
The full-body scanners show a person's contours on a computer in a private room removed from security checkpoints.
But critics say they amount to virtual strip searches.
Some have complained that the new enhanced pat-downs are humiliating and intrusive, too.