RedDrop malware is a recently discovered mobile threat that can steal data from infected devices and also record ambient audio.

Security researchers at Wandera have spotted a new sophisticated family of mobile malware dubbed RedDrop that can steal data, record audio, and intercept SMS. All data stolen from infected systems is uploaded to remote file storage systems.

The malicious code was found in dozens of apparently innocuous apps, the researchers discovered RedDrop hidden in 53 Android applications, including image editors, calculators, language learning apps and space exploration apps.

The applications work as expected and the RedDrop malware is executed in the background.

“The latest zero-day threat to be discovered by Wandera’s mobile threat research team is RedDrop, a family of mobile malware inflicting financial cost and critical data loss on infected devices.” reads the analysis published by Wandera. “The most worrying part? The 53 malware-ridden apps are exfiltrating sensitive data – including ambient audio recordings – and dumping it in the attackers’ Dropbox accounts to prepare for further attacks and extortion purposes.”

Once an infected app is installed, it downloads at least seven more Android Application Packages (APKs) from a different command and control server, each of them implements a malicious functionality. The APKs are stored in the memory of the device, this trick allows to execute them without including the feature in the original malware sample.

The RedDrop malware could also send SMS message to a premium service and then instantly deletes the message to avoid detection by the user.

The researchers discovered that the malicious Apps are distributed from a complex network composed of more than 4,000 domains registered to the same underground group that might be operating out of China.

“Wandera’s machine learning detections first uncovered one of the RedDrop apps when a user clicked on an ad displaying on popular Chinese search engine Baidu.” continues the analysis. “The user was then taken to huxiawang.cn, the primary distribution site for the attack. The landing pages that follow host various content to encourage and incite the user to download one of the 53 apps within the RedDrop family of malicious apps.”

One of the applications observed by the researchers (CuteActress) was designed to send an SMS message to a premium service every time the user would use a functionality of the app. The threat would also delete all of these messages, thus erasing any evidence of these premium SMS.

Currently, most of the infections were observed are in China, followed by Europe and America.

Android users that download apps from third-party sources and websites are most exposed to this threat, no instance of the RedDrop malware have been yet found on the Google Play store neither other official stores.

Pierluigi Paganini

(Security Affairs – RedDrop, Android malware)

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