Shortly after midnight on Jan. 28, desperate Egyptian authorities effectively pulled the plug on the Internet amid a wave of protests roiling the government of Hosni Mubarak.

To many, the unthinkable had happened.

The global computer network was supposed to be resilient in its architecture, featuring multiple different pathways to allow Internet users to circumvent choke points. If the Internet could be cut off in minutes to virtually all of Egypt — by many measures a technologically developed nation — people started wondering whether it could be shut down in the United States, too.

Experts say that it may be technically possible. However, only a fool in the Oval Office would take such irrational steps.

Still, revelations about torture at Guantanamo and domestic spying and wiretapping after Sept. 11 have created a heightened sense of anxiety about giving the federal government more leeway to intrude or restrict behavior in times of conflict.

While there are thousands of Internet service providers in the U.S., there are only a dozen or so “Tier 1 ISPs” — the providers that carry the bulk of Internet traffic around the country. Shutting down those companies would kick about 80 percent of Americans off the Web, said Jonathan Zittrain, a Harvard Law School professor who also teaches computer science at the university.

“Imagine the government went completely off the rails, and someone went thundering around and said, ‘Do X,’” Zittrain said. “Ten phone calls to Internet service providers who can’t say no would make the Internet virtually inaccessible to the vast majority of people in the country.”

Many politicians and government officials dismiss as “unrealistic” the idea of the government silencing the Internet in the U.S.

“There would be real, practical obstacles to doing that because our infrastructure is much more widely dispersed and developed,” former Homeland Security Secretary Michael Chertoff told POLITICO. “Nor do I think it would be a political possibility. It is unrealistic for the U.S., thank God.”

Still, in the last Congress, mere talk of including an Internet “kill switch” for the White House effectively torpedoed cybersecurity bills in the Senate. A 2009 bill sponsored by Sens. John Rockefeller (D-W.Va.) and Olympia Snowe (R-Maine) included a passage to give the president emergency control of the Internet but prompted a public outcry and was revised.

Then, a trio of lawmakers — Sens. Joe Lieberman (I-Conn.), Tom Carper (D-Del.) and Susan Collins (R-Maine) — introduced a different cybersecurity bill and argued for months that it did not contain a “kill switch.” In February, however, they unveiled a new version of the bill that specifically bars the president from shutting down the Internet.

“There is no so-called kill switch in our legislation because the very notion is antithetical to our goal of providing precise and targeted authorities to the president,” Lieberman said on the day he introduced the Cybersecurity and Internet Freedom Act.

Added Collins, “While experts question whether anyone can technically ‘shut down’ the Internet in the United States, our bill has specific language making it crystal clear that such actions are expressly prohibited.”

Egyptian authorities most likely used an alternate method to cut off Internet exchange points, or IXPs, than the one outlined by Zittrain, according to a study by Bill Woodcock, research director for Packet Clearing House, a nonprofit research institute that analyzes Internet traffic.

Internet exchange points act like hubs by connecting different service providers and allowing for the exchange of Internet traffic between their networks, ultimately allowing consumers to connect, Woodcock said.

Most of Egypt’s Internet traffic crossed at a central exchange point in downtown Cairo, said Woodcock, and Egyptian authorities simply shut it off.

The U.S. has many more exchange points — 84, in fact — according to Packet Clearing House. But deactivating just one would substantially slow the Internet because there’s not much excess capacity at each one, Woodcock said.

Zittrain said the Internet also might be disabled by using malware — viruses, worms or other malicious codes — to disrupt routers.

Even if the Internet can technically be shut down in the U.S., the larger roadblock is surely political. It’s something on which Republicans and Democrats agree: An Internet shutdown would be as foreign to U.S. citizens as a coup. It’s not going to be tolerated by BlackBerry-reliant business executives, text-happy teens and everyone in between.

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