Security Experts:

XcodeGhost Malware Updated to Target iOS 9

The XcodeGhost compiler malware designed to target iOS and OS X users is still active and its developers have continued to improve their creation, FireEye warned on Tuesday.

The existence of XcodeGhost was brought to light in mid-September by Chinese developers, and the threat was later analyzed by several security firms, including Palo Alto Networks and FireEye. The malware allows attackers to perform various actions, such as collecting information from infected devices and opening arbitrary websites.

Attackers have distributed the malware with the aid of modified versions of the Apple Xcode development platform, which they posted on various Chinese websites knowing that developers in that country prefer third-party sources over Apple’s official servers due to slow download speeds.

While no malicious OS X apps have been seen in the wild, experts reported finding thousands of iOS apps infected with XcodeGhost, many of which made it to Apple’s official app store.

Apple quickly took steps to remove the malicious apps and prevent further infections. However, FireEye says the threat is still partially active and has made its way to enterprise users. The malware has mainly targeted China, but most of the 210 enterprises running XcodeGhost-infected apps are in Germany (62%) and the United States (33%), mainly in the education sector.

These infected applications have made more than 28,000 attempts to connect to their command and control (C&C) servers. While these servers are no longer controlled by the attackers, FireEye warns that they can be hijacked by threat actors.

The developers of popular applications whose products made it to the App Store infected with XcodeGhost have released updates to replace the rogue versions, but many users haven’t installed them. In the case of WeChat, one of the most popular infected apps, FireEye has counted nearly 3,000 users still utilizing the infected version.

“Some enterprises have taken steps to block the XcodeGhost DNS query within their network to cut off the communication between employees’ iPhones and the attackers’ CnC servers to protect them from being hijacked. However, until these employees update their devices and apps, they are still vulnerable to potential hijacking of the XcodeGhost CnC traffic -- particularly when outside their corporate networks,” FireEye explained.

Of the infected iPhones observed by the security firm, 10 percent are running iOS 7, 65 percent are running iOS 8, and 35 percent are running iOS 9.

In iOS 9, a version of the mobile operating system released in mid-September, Apple introduced a new security feature designed to prevent apps from connecting to a server insecurely, over HTTP. This prevented XcodeGhost from connecting to its C&C servers.

However, the malware’s developers released a new version, dubbed by FireEye “XcodeGhost S,” which uses the possibility to add exceptions to this rule, ensuring that the threat can also be executed on iOS 9.

Additionally, XcodeGhost S is designed to construct the name of the C&C domain by concatenating the final string character by character. This helps the malware bypass static detection.

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Eduard Kovacs (@EduardKovacs) is a contributing editor at SecurityWeek. He worked as a high school IT teacher for two years before starting a career in journalism as Softpedia’s security news reporter. Eduard holds a bachelor’s degree in industrial informatics and a master’s degree in computer techniques applied in electrical engineering.