~Dissecting Malware
// f0wL's Blog about malware analysis and reverse engineering
~Dissecting Malware

Jamba Superdeal: Helo Sir, you want to buy mask? - Corona Safety Mask SMS Scam

As if there wasn't enough pain and suffering in the world already because of COVID-19 some criminals still try to piggyback on the fear of others. A quick look at an Andorid SMS "Worm".

Since the current COVID-19 outbreak is getting masively taken advantage of by various cybercriminals I thought it would be a good opportunity to try out Android reverse engineering. Let's dive right in:


Webpage


The following dynamic part of this analysis was done in VirtualBox with the most recent Version of Android-x86. For those playing along at home: The Setup is really simple (as Live Booting is sufficient). Just remember to crank up the Video Memory, change the Graphics Controler to VBoxVGA and enable 3D Acceleration as otherwise the VM will only boot to a command prompt.

Installation


During the installation process there are no permissions to be granted to it.

Installation


Before finishing the installation there is a Google Play Protect warning already. I'm not sure if this is a signature based detection or actually based on the expected behaviour while parsing the package. I'll install it anyway.

Google Play Protect


After opening "Corona Safety Mask" for the first time it will ask for the permission to access the user's address book.

Contacts Permissions


And secondly it requires the permission to send SMS messages as well. This should be a red flag to users in general if the request is made without any notice as to why this permission is required (e.g. a second factor authentication). Scams like this can get very expensive for the user which is probably also one of the major goals of this malware.

SMS Permissions


Below you can see the main (and only) view of the app. Questionable content, more typos... red flags everywhere, but some people might just be desperate enough to fall for it.

App


For static analysis of the apk File I'll be using jadx-GUI. Below you can find the Github Repository.


It works very well for my purposes here and it even has a dark mode 😎

Jadx Decompiler


Upon tapping the "Get Safety Mask" button in the app it will direct you to a second website called Masksbox which might be part of a larger scam setup.

Weblink


When I visited the page this morning it was displaying this downtime message. A quick check via archive.org didn't return a recent snapshot of the page.

Masksbox down


A few hours later the website was back up with a partialy configured Wordpress CMS. The Navbar makes it quite obvious that the page is still being built.


Masksbox


Of course there can't be a malware sample without at least one funny typo. Here we can also see that the app is using the EasyPermissions wrapper library to handle contacts and SMS functionality.

Permissions Typo


This section of the code is responsible for reading the contents of the victims address book and writing them to a list.

Reading Contacts


Depending on the size of the contacts list it will either start at a random index and work its way up if there are over 100 contacts in the list or it will just send a SMS to all contacts if there are less than 100 in the list.

Webpage


Lastly we can take a look at the signature of the APK. It was signed with the CN "Hemant Prajapat", but that is a fake name for sure. Other than that there's not much interesting info to get from this.

APK Signing


And that's it! In times like this it is especially important to keep your means of communication safe, so better be extra careful. Stay home, stay safe (on the interwebs) and most importantly: stay healthy (applies to you and your devices).

IOCs

CoronaSafetyMask

CoronaSafetyMask.apk --> SHA256: 8a87cfe676d177061c0b3cbb9bdde4cabee0f1af369bbf8e2d9088294ba9d3b1
                         SSDEEP: 24576:KjQEzqDqCXaTJwv2AbxMHKR+ZCGPEmD8oJxmLaRyiLQuZgvNwN:wqDjaNcdRNw8+xm2RFEuZgvNk

URLs

hxxp://coronasafetymask[.]tk
hxxp://masksbox[.]com



About me

Hey there! My Name is Marius Genheimer aka f0wL and I'm a Computer Science Student from Germany. As you can probably tell I like to analyse malware (especially Ransomware) in my spare time.

https://ransomware.email

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An automated analysis platform based on the Cuckoo Sandbox. Feel free to drop your samples!

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