New Android trojan targeting over 60 banks and social apps

Cengiz Han Sahin, Wesley Gahr, September, 2017

Increased threat for Android users

Since the beginning of this year, SfyLabs' threat hunters have discovered several Google Play malware campaigns using new modi operandi such as clean dropper apps that effectively evaded all antivirus and Google Play protection solutions (Bouncer & Protect) for months. Unfortunately this was not the only threat this year. Android actors such as ExoBot have also been very busy adding Remote Access Trojan capabilities (SOCKS5 and VNC) to their software in their attempt to evade fraud detection solutions of financial organizations that mainly rely on IP-based geolocation and device binding vectors.

The shift of malware campaigns from desktop (Windows) to mobile (Android) seems largely related to the fact that these days most transactions are initiated from mobile devices instead of the desktop. This motivates actors to invest in developing solutions that target Android and have the same capabilities as the malware variants that have been evolving on the desktop for years.

New Android banking trojan: Red Alert 2.0

Red Alert 2 Android banking trojan
The last several months a new actor has been very busy developing and distributing a new Android trojan dubbed "Red Alert 2.0" by the actor. The bot and panel (C&C) are fully written from scratch, while many other trojans are evolutions of leaked sources of older trojans.

Red Alert has the same capabilities as most other Android banking trojans such as the use of overlay attacks, SMS control and contact list harvesting. There are however also other functions that have not been seen in other Android banking trojans.

New attack vectors

New attack vectors
Red Alert actors are regularly adding new functionality, such as blocking and logging incoming calls of banks (see image below), which could affect the process of fraud operation departments at financials that are calling users on their infected Android phone regarding potential malicious activity.

Forum post of Red Alert actor on bot update
Forum post of Red Alert actor on bot update

Another interesting vector is the use of Twitter to avoid losing bots when the C2 server is taken offline (NTD). When the bot fails to connect to the hardcoded C2 it will retrieve a new C2 from a Twitter account. This is something we have seen in the desktop banking malware world before, but the first time we see it happening in an Android banking trojan.

All these parts are under development but it gives the reader a good idea of the mindset of the actors behind Red Alert 2.0 as a new Android bot.

Technical details
The following code flow is triggered when the C2 of Red Alert is unavailable (connection error):

1) Red Alert Android bot has a salt stored in strings.xml
Salt stored in strings.xml

2) The following code uses the current date combined with the salt to create a new MD5 hash of which the first 16 characters are used as a Twitter handle registered by the Red Alert actors (i.e. d8585cf920cb893a for 9/18/2017).
Twitter handle

3) The bot then requests the Twitter page of the created handle and parses the response to obtain the new C2 server address.
C2 server address

Overlay attack targets

The interesting part of the overlay attack vector for this malware is that the targets are stored on the C2 server and the list is not sent back to the bot, making it more work to retrieve the list compared to other Android banking trojans. The following list is not complete but gives a good overview of most of the overlay HTML the actor has bought and developed:

Overlay attack mechanism

Upon opening an application that is targeted by Red Alert an overlay is shown to the user. When the user tries to log in he is greeted with an error page. The credentials themselves are then sent to the C2 server. To determine when to show the overlay and which overlay to show, the topmost application is requested periodically. For Android 5.0 and higher, the malware uses Android toolbox, which is different from the implementation used by other Android trojans such as Mazar, Exobot and Bankbot.

v0_3 = Runtime.getRuntime().exec("/system/bin/toolbox ps -p -

P -x -c");
BufferedReader v1 = new BufferedReader(new
v2 = new ArrayList();
v3 = new ArrayList();
while(true) {
String v4 = v1.readLine();
if(v4 == null) {

Bot Operations

The C2 server can command a bot to perform specific actions. The commands found in the latest samples are listed below:

a.a = new a("START_SMS_INTERCEPTION", 0, "startSmsInterception");

a.b = new a("STOP_SMS_INTERCEPTION", 1, "stopSmsInterception");
a.c = new a("SEND_SMS", 2, "sendSms");
a.d = new a("SET_DEFAULT_SMS", 3, "setDefaultSms");
a.e = new a("RESET_DEFAULT_SMS", 4, "resetDefaultSms");
a.f = new a("GET_SMS_LIST", 5, "getSmsList");
a.g = new a("GET_CALL_LIST", 6, "getCallList");
a.h = new a("GET_CONTACT_LIST", 7, "getContactList");
a.i = new a("SET_ADMIN", 8, "setAdmin");
a.j = new a("LAUNCH_APP", 9, "launchApp");
a.k = new a("BLOCK", 10, "block");
a.l = new a("SEND_USSD", 11, "sendUssd");
a.m = new a("NOTIFY", 12, "notify");
a.o = new a[]{a.a, a.b, a.c, a.d, a.e, a.f, a.g, a.h, a.i, a.j, a.k, a.l, a.m};


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Update Google Market
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Package name: com.aox.exsoft
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Update Flash Player
Package name: com.aox.exsoft
SHA-256: dc11d9eb2b09c2bf74136b313e752075afb05c2f82d1f5fdd2379e46089eb776

Update WhatsApp
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Android Update
Package name: com.aox.exsoft
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Package name:
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Android Update
Package name:
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