A group of researchers from Georgia Tech have created a way to inject malicious code into apps in such a way that allows the code to look innocuous running in the test environment, be approved and signed, and then later be turned into a malicious app.

The researchers created an app that operated as a Georgia Tech “news” feed. The malicious code was distributed throughout the app as “code gadgets” that were idle until the app received the instruction to rearrange them. “After the app passes the App Review and lands on the end user device, the attacker can remotely exploit the planted vulnerabilities and assemble the malicious logic at runtime by chaining the code gadgets together”, they write.

The researchers continue that “despite running inside the iOS sandbox, [the] Jekyll app can successfully perform many malicious tasks, such as stealthily posting tweets, taking photos, stealing device identity information, sending email and SMS, attacking other apps, and even exploiting kernel vulnerabilities.”

“The message we want to deliver is that right now, the Apple review process is mostly doing a static analysis of the app, which we say is not sufficient because dynamically generated logic cannot be very easily seen,” Lu told Technology Review.