Hackers are taking advantage of vulnerability in Apple's iOS mobile operating system to install malicious software disguised as popular apps such as Facebook, Twitter and WhatsApp to

steal personal information. The installation happens when a user clicks a link that may have been sent to them via email, text message or even a fake advert on a website, according to a new

report by cybersecurity firm FireEye. A fake and malicious app is installed that looks like the legitimate version on a user's device. And unlike the normal version of the app, the

hacker's version can steal sensitive information and send it back to a remote server. "It can look at the historical data that app might have saved depending on the type of

apps being used for malicious purposes, according to FireEye. The hack could potentially be used on different mobile operating systems but so far FireEye has only seen it employed on iOS

version 8.1.3 and before. This particular hack also works on iOS devices that haven't been modified to bypass certain restrictions imposed by Apple -- which were typically seen as safe

from attack. Apple has fixed the problem, according to sources close to the situation who do not wish to be named due to the sensitivity of the situation. This attack was discovered from the

400GB worth of files leaked when an Italian company that sells surveillance technology to governments was hacked last month. The data dump from Hacking Team is likely to lead to more severe

attacks, according to FireEye, which many are not prepared for. "It is a glimpse under the water to see the rest of the iceberg," Mullis said. "You can be sure that not only

are there major institutions currently breached and that don't know about it, but there are other groups using attacks against end users." _Clarification: This article has been

updated since first published to provide further information to Apple's response. _