The Saudis are desperate to keep what's happening in Iraq from happening in their country. CBS News was given an extraordinary look at what they're doing.
We flew over the Arabian Desert to see the new, 600-mile long border fence that's protecting Saudi Arabia from ISIS. On the other side is the chaos of Iraq, where ISIS is waging a brutal war.
The Saudis are using radar and infrared cameras to make sure it doesn't spill across the frontier.
However, the impressive border fence may not be enough to keep ISIS out of Saudi Arabia because hundreds of young Saudi men are fighting with ISIS in Iraq and Syria.
Saudi officials fear that, like al Qaeda before it, ISIS will radicalize Saudis, who'll then target their own government.
Saudi officials took us to the maximum security prison where they hold convicted terrorists. "Some of them are coming from Syria, some from Iraq," one Saudi official said.
And Saudi Arabia's special forces showed us their ability to repel terrorist attacks -- including plane hijackings and villages infiltrated by violent extremists.
Dozens of Saudis have blown themselves up in ISIS suicide bombs. With the explosives rigged up at a safe distance, Lt. Col. Husam Al-Shethry showed us the devastation they cause.
Gen. Mansour Al-Turki told us ISIS is a bigger threat than al Qaeda ever was.
"The reality is, they have their ambitions to have a larger area under their control," Al-Turki said. "Including Saudi Arabia, of course."
The Saudi authorities have cracked down on mosques and Muslim clerics that were radicalizing young men. But that hasn't stopped hundreds of Saudis from joining ISIS. Saudi officials told us the recruitment has moved online and claim they're sometimes powerless to stop it.