Was Fake AP Terror Tweet a Criminal Act?

computer hacker hacking cyber security
John Lund | Blend Images | Getty Images

It's amazing the kind of trouble you can get into with 140 characters or less.

On Tuesday at 1:07 p.m., someone gained unauthorized access to the Associated Press's Twitter account to report that President Barack Obama had been injured in a pair of explosions at the White House. The news was fake, but the momentary panic and legal aftershocks are both very real.

(Read More: Markets Plunge Briefly on Fake AP Terror Tweet)

"Hacking in [to @AP's account] and sending out a tweet [of this nature] is a federal crime," said Joel Reidenberg, a Fordham Law School professor.

While the hacking act itself is a clear-cut violation of law, the content of the message itself could also be interpreted as designed to incite panic or lawless action, which some constitutional lawyers said could also be viewed as illegal and possibly criminal.

"In this case, it's very much like screaming fire in a theater," Reidenberg said. "Making a statement designed to incite panic: Does it create an imminent public danger? The answer is probably yes given the nature of the message."

And to be sure, it did cause panic, at least on Wall Street.

While the Tweet was only viewable for a few minutes, it was retweeted thousands of times, and once the message hit trading floors, it got even worse.

(Read More: Fake Tweet Causes 4 Minutes of Panic on Trading Floors)

In the moment following the false Tweet, the Dow Jones Industrial Average plummeted more than 100 points (it quickly snapped back after the report was debunked). In those moments, more than $130 billion in value were wiped out on the S&P 500, according to Reuters data.

In addition to criminal liability, such massive losses would also likely expose the AP hacker to civil suits from traders and investors caught on the wrong side of that market see-saw.

Whether the AP hacker will ever be identified however, is a different story. The web is chock full of "tweet-and-runs" like this one, and very few have been publically identified, let alone prosecuted.

—By CNBC's Jesse Bergman; Follow him on Twitter: @JBergmanCNBC

email: tech@cnbc.com