The first major outbreak of malware has been found in Apple’s own iOS App Store, the vendor has disclosed. It is now working to remove the malicious code that could have infected 344 legitimate applications for the iPad and iPhone.

The Apple store has been attacked before, but never on this scale. Only five malicious apps had previously been found in the App Store, according to security firm Palo Alto Networks, which has now found rogue code that has been embedded in hundreds of legitimate applications. The malware, dubbed XcodeGhost, has a limited potential for damage and resulted in no reported incidents of theft, according to security expert Ryan Olson, Palo Alto Networks’ Director of Threat Intelligence.

However, Ryan described the significance of the break in as ‘a pretty big deal’ as it proves that the App Store can be compromised. Hackers are thought to have gained entry to the App store by infecting the machines of legitimate software developers. A new wave of attacks could be launched by criminals using this approach and it will be hard for the App Store to defend itself against, according to Ryan, who said developers are now a ‘huge target’.

The hackers had convinced developers of legitimate software to use a corrupted counterfeit version of Apple’s Xcode software for creating iOS and Mac apps. Developers may have been tempted to source the tainted version of Xcode, from a server in China, because it downloaded much faster than software from Apple’s US servers.

“We are working with developers to make sure they use the proper version of Xcode to rebuild their apps,” said Apple spokeswoman Christine Monaghan.

Meanwhile any applications, which are known to have been created with the infected Xcode software, have been removed from the App Store. Researchers said infected apps included popular mobile chat app WeChat, car-hailing app Didi Kuaidi and a music app from NetEase.

Apple has not released any guidelines on how users can assess if the software has infected their iPhones or iPads. Apple has declined to say how many apps it had uncovered.

Chinese security firm Qihoo360 Technology claimed to have found 344 apps tainted with XcodeGhost.