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May 7th, 2014

Fake government ransomware holding Android devices hostage

Ransomware, which has already made its rounds on Windows, is now increasingly targeting the Android operating system. A new piece of mobile malware claiming to be the government under the name Android: Koler-A is now targeting users.

We have full control of your phone – give us $300 and we’ll give it back

Obrázek 1-1

The ransomware is pushed automatically from fake porn sites visited by Android users via a malicious .apk file that appears in the form of an app. The innocent appearance of the app deceives users and is a powerful social engineering tactic used by malware developers to trick people into installing malicious apps. The form of delivery is not the only thing that makes the app suspicious and potentially dangerous, but the access it seeks are highly unusual and alarming. The ransomware requests full network access, permission to run at startup and permission to prevent the phone from sleeping. Once installed the granted access allows the ransomware to take control of the device. The full network access allows the malicious app to communicate over the web and download the ransom message that is shown on the captive device. The permission to run at startup and prevent the phone from sleeping fully lockdown the phone, preventing victims from escaping the ransom message.

The ransomware localizes fake government messages, depending on the users GPS location, accusing them of having viewed and downloaded inappropriate and illegal content. What does the ransomware do next? Demands ransom of course! The ransom to regain access to the device including all of its apps, which it claims are all encrypted, is set at around $300 and is to be paid through untraceable forms of payment such as MoneyPak.

avast! Mobile Security safeguards against ransomware

Both AVAST’s free and premium mobile security apps, avast! Mobile Security and avast! Mobile Premium, protect customers from falling for the devious apps containing ransomware. AVAST detects this ransomware under the name Android: Koler-A and blocks its execution.

We recommend that everyone be cautious when downloading apps, especially from unofficial app markets. We also urge users to not open any files that have been downloaded to their device without their consent. Always check what apps want to access and in addition to being cautious, we advise people download antivirus to protect their devices. This new ransomware appearing on Android is the perfect example of how malware is starting to move away from the PC environment and into our pockets and there are no signs of this slowing down.

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March 31st, 2014

The Gray-zone of malware detection in Android OS

Does the title of this blog post have a mysterious meaning? Not exactly.

In this first part about the gray-zone of Android malware detections, I will introduce the Android:SecApk, a detection regarding the protection that the App Shield (Bangcle) offers to Android applications (.apk). This detection has a big sample set that is still growing. Some SecApk wrapped samples that existed or still exist in the Google Play Store and third party stores, can be seen in the table below.

MD5

Name \ Info

F1EF5B8C671B2146C2A2454ECF775E47

G锁屏冰雪奇缘之来自星星的你V1.0.apk

\ PUP – An application to promote a specific movie. Potentially unwanted because of the extended permissions that was requested.

Current Status: Removed from Google Play

10bd28d4f56aff83cb6d31b6db8fdbd2

Cut_the_bird.apk

\PUP – A game that have potentially unwanted permissions that they can drive to loss of private personal info.

05ffb6f34e40bb1cf8f9628e5647d5e3

aini1314langmanzhutisuoping_V2.5_mumayi_700e0.apk

\PUP – A screensaver application that has permissions unrelated with the purpose of the app.

d6b40bbb79b54c09352a2e0824c0adba

3D职业乒乓球.apk

\Pup – This application is a tennis game. Potentially unwanted because of the extended permissions that was requested.

eefd2101e6a0b016e5a1e9859e9c443e

eefd2101e6a0b016e5a1e9859e9c443e.apk

\Malware – This app steal personal data and SMS messages from the user.

 

The App Shield is an online service that, after a submission of an .apk, encrypts it and adds some layers of protection. The procedure of the encryption and protection of the apk will be discussed with more detail during the course of the second part of this blog post.

Starting with the submission process, a clean app named AvstTest.apk uploaded to the service. The exported .apk was renamed as AvstTest[SecApk].apk. In addition, apktool and dex2jar used accordingly to decode the .apk resources and convert the ‘.dex’ files to ‘.jar’.

Folder structure

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