Android Malware Uses Built-In Firewall to Block Security Apps

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Malware authors employ open-source Android firewall utility to block security app from talking to their cloud servers.Even if some malware families never get to cause worldwide damage, it’s sometimes interesting to read about new techniques that some malware authors employ for creating their threats.

One of the most recent cases is a malware family that targets Android devices in China, discovered by Symantec, and named Android.Spywaller.

The uniqueness of this threat is the fact that during infection, the malware looks for Qihoo 360, a popular security app among Chinese Android users.

Android.Spywaller uses a firewall to block Qihoo 360 internal communications

The malware searches and registers on the device with the same UID (unique identifier) used by the Qihoo 360 app, and then loads a binary called DroidWall, a version of the UNIX iptable package, modified to run on Android devices.

The iptable package is a well-known firewall utility for Linux systems, and DroidWall was developed by independent security researchers Rodrigo Rosauro, who later sold it to AVAST in 2011. Since the app spent a few years as open source, malware authors can still find it via Google Code or GitHub repositories.

Just like in Android.Spywaller’s case, DroidWall can be used to block security applications from communicating with their cloud-based threat analysis servers, rendering the security apps useless, and giving the malware free and unscathed access to the device.

Android.Spywaller infects devices by posing as a Google app

Symantec researchers say that the malware is not a very common infection among Chinese users, so there’s nothing to worry about just yet.

To infect users, the malware poses as a Google app called “Google Service,” taking advantage by the lack of an official Google Play Store in the country. (There is no official Google app called Google Service.)

Spreading via unofficial Android app stores and fooling users into giving it admin permissions, Android.Spywaller goes on to work in the phone’s background, stealing information from the device, and then uploading it to one of its command servers.

One of the most complete Android spyware families ever discovered

Symantec reports that the app will search and exfiltrate, data such as call logs, SMS, GPS readings, system browser data, emails, radio, images, and contact lists.

Additionally, the app also gathers data from other apps such as BlackBerry Messenger, Oovoo, Coco, QQ, SinaWeibo, Skype, Talkbox, TencentWeibo, Voxer, Wechat, WhatsApp, and Zello.

Researchers say that Android.Spywaller is one of the most intrusive spyware families they’ve found, the malware covering multiple data types and sources of information at once.

Android.Spywaller hiding as Google Service app

Android.Spywaller hiding as Google Service app