NEW YORK —
Others, like Saluzzi, think computers may have sold on the tweet itself. That's possible because computer trading programs are increasingly written to read, and react to, news from social media outlets like Twitter.
Experts say the fake tweet seemed designed to catch a computer's attention.
Rich Brown, head of Elektron Analytics, a Thomson-Reuters unit that sells news feeds that computers can read, said that the words "explosions" or "Obama" alone wouldn't have triggered selling. But add "White House," and it's a combination even the slowest computer couldn't miss.
Brown said his service doesn't include Twitter in its feeds because there's too much useless "noise" in the deluge of tweets and, given the 140-character limit to tweets, often too little context.
Before the fake tweet appeared on Tuesday, it looked like any other good day on Wall Street. Unexpectedly strong earnings reports sent stocks in the Dow Jones industrial average up 1 percent to 14,697 with three hours to go in the trading day.
Then, at 1:08 p.m. EDT, a tweet appeared on the hacked AP Twitter account stating that two explosions at the White House had injured President Barack Obama. Stocks immediately started falling and tumbled for two minutes.
The Dow dropped from 14,697 to 14,554, losing 143 points, or 1 percent. In the frenzied selling, oil prices dropped, gold rose, the dollar rallied and the price of Treasury notes, seen by many investors as a hiding spot, shot higher, briefly knocking yields to their lowest level of the year.
The AP quickly announced that its account had been hijacked and the report was false. The Dow began to climb again, recovering all its losses by 1:18 p.m. That was 10 minutes after the fake tweet, according to FactSet, a financial data provider.