A popular mobile ad library used by multiple Android apps poses a severe malware threat, researchers at infosec firm FireEye have warned. The security researchers said that altogether 200 million affected apps had been downloaded.
This ad library aggressively collects sensitive data and is able to perform dangerous operations such as calling home to a command-and-control server before downloading and running secondary components on demand.
Mobile ad libraries are third-party software included by host apps in order to display ads. Because this library could potentially be used to conduct large-scale attacks on millions of users, FireEye refers to it anonymously by the code name “Vulna” rather than revealing its true identity.
An analysis of the most popular apps (those with over one million downloads) on Google Play reveals that 1.8 per cent of them used "Vulna". The potentially affected apps have been downloaded more than 200 million times in total.
FireEye catalogues a variety of built-in aggressive behaviours which, in addition to vulnerabilities with the technology, make Vulna a threat.
Though it is widely known that ad libraries present privacy risks such as collecting device identifiers (IMEI, IMSI, etc.) and location information, Vulna presents far more severe security issues. First, Vulna is aggressive - if instructed by its server, it will collect sensitive information such as text messages, phone call history, and contacts. It also performs dangerous operations such as executing dynamically downloaded code.
Second, Vulna contains a number of diverse vulnerabilities. These vulnerabilities, when exploited, allow an attacker to utilize Vulna’s risky and aggressive functionality to conduct malicious activity, such as turning on the camera and taking pictures without the user’s knowledge, stealing two-factor authentication tokens sent via SMS, or turning the device into part of a botnet.
A blog post by FireEye warns that Vulna is also "plagued with various classes of vulnerabilities that enable attackers to turn Vulna’s aggressive behaviours against users".
Security shortcomings of the software include its use of unsecured HTTP for receiving commands and the dynamic loading of code from its control server.
FireEye said that it has notified both Google and the developer of the software about the threat.
"We've notified both Google and the vendor of the ad library and given them the list of apps which are impacted by these issues," Dr Tao Wei, a senior research scientist at FireEye, told El Reg. "They have confirmed the issues and are actively working on addressing these issues. The vendor of the ad library is in the process of notifying the developers using their library to upgrade to the latest version which fixes many of the security issues we addressed.
"In the meantime, detailed information will be provided to FireEye's customers to protect them from potential attacks."
We asked Google for comment on Monday but are yet to hear back. We'll update the story as and when we hear more. ®