In response to a question from John McCain, a DHS official said that some ISIS "adherents" were saying on Facebook and Twitter that they should infiltrate the U.S.-Mexico border.
Francis Taylor, under secretary for intelligence and analysis at DHS, told senators during a hearing that ISIL supporters are known to be plotting ways to infiltrate the United States through the border.
“There have been Twitter, social media exchanges among ISIL adherents across the globe speaking about that as a possibility,” Taylor told Sen. John McCain (R., Ariz.) in response to a question about “recent reports on Twitter and Facebook of messages that would urge infiltration into the U.S. across our southwestern border.”
“Certainly any infiltration across our border would be a threat,” Taylor said, explaining that border security agents are working to tighten measures that would prevent this from taking place.
“I’m satisfied we have the intelligence and the capability on our border that would prevent that activity,” Taylor said.
As with many other issues, this one falls under the category of "stay vigilant and don't overreact."