@SkyWhisperer - I didn’t realize that the fifth columnist definition hearkened back to the days of the Spanish civil war.
I now understand what is meant by “column.” I had heard its usage in popular culture but didn’t know the etymology. Like you said however the concept is not in itself new. It just took on a military context.
If you want to know what I fear most, however, it’s not the spy rings. It’s the computer hackers who have attacked vital U.S. information resources. They do it remotely, but it’s quite possible some of them could get visas and work in our most trusted national security interests near Washington, D.C.
They would be fifth columnists with the most strategic access to carry on high level information warfare attacks, from the inside out in my opinion.