The malware was first discovered by a user posting in the Apple support forums who noted that a download of Instaquotes-Quotes Cards For Instagram from developer Ilyas Hassani triggered warnings from the ClamXav antivirus software for Mac. While the Windows malware obviously could not harm the user's OS X installation, it was flagged as an infected file posing a danger to Windows systems. After learning about the discovery, CNET performed additional testing on the download to confirm that it was not a false positive.
Since the downloaded .ipa file is a package, these executables could be extracted using the package manager Pacifist, and then more accurately scanned. Afterward, other malware programs like Sophos that initially missed detecting the malware instantly picked it up and described it as "Mal/CoiDung-A," a worm written in visual basic that installs files within the Windows system directory and then modifies the Windows registry to execute the malware when the system is restarted.It is unclear exactly how or why the malware came to be included in the App Store package, but it seems almost certain to have been an accidental inclusion. As delivered inside the application package, it appears to pose no harm to Windows users, who would have to decompress the package and manually run the infected file in order to expose themselves to the malware.
Copying the malware to a Windows virtual machine running the latest version of Microsoft Security Essentials resulted in the malware being immediately detected and removed from the system.
The infected application debuted in the App Store on July 19 and is currently still available for download after a temporary price drop from $0.99 to free over the weekend.