Hackers threw US money markets into chaos yesterday when they took control of the Associated Press Twitter account and tweeted that two explosions at the White House had injured President Obama. After the Boston bombings, it wasn't hard to believe and it only took minutes for a reaction.
The Dow Jones Industrial Average fell more than 150 points but recovered quickly when found to be false. The Dow measures the financial performance of 30 major US companies and is often used as a measure of the overall health of the wider stock market.
They have something called 'automatic electronic trading' - robots that troll news headlines - and there is speculation that this is what caused the dramatic sell-off.
A group called The Syrian Electronic Army, who support Syria's leader Bashar Al-Assad, later claimed responsibility. They also claim to have hacked the BBC, Agence France-Presse, Football World Cup, FIFA and many more.
Twitter is being blamed for the meltdown for not insisting on a two-step log-in process and they are currently hiring software engineers to fix it. Meanwhile the White House intends to push through legislation to address the issue of cyber attacks which are now getting well and truly out of hand.
But this time it's more serious. They proved a very important point - just how easy it is to manipulate the US stock market.