The Dow Jones briefly plummeted yesterday after hackers took control of the Associated Press's Twitter account and used it spread a bogus claim that the White House had been hit by a terrorist attack.
At 1.07pm Eastern Time, AP's Twitter account told its 1.9 million followers: "Breaking: Two Explosions in the White House and Barack Obama is injured."
The tweet sparked a sell off on US markets, with the Dow Jones Industrial Average dropping 145 points, or 0.9%, wiping around $130 billion off the value of stocks.
However, with an AP reporter quickly informing followers that the offending tweet was bogus, the market recovered in minutes. AP suspended its account, although it has now been reinstated, minus its followers.
The self-styled 'Syrian Electronic Army' has claimed responsibility for the hack, the latest in a series that have hit the BBC and football governing body Fifa, among others.
Twitter is already planning to introduce two-factor authentication for access to accounts, making it harder for people to hijack handles even if they have passwords.
Social media's relationship with the markets is increasingly close; earlier this month Bloomberg integrated real-time Twitter feeds into its market data terminal while the SEC has also moved to allow companies to use social media for corporate disclosures.