BeatBanker A dual‑mode Android Trojan

src/mobile-pentesting/android-app-pentesting/README.md

@@ -57,6 +57,61 @@ java -jar ../APKEditor.jar m -i splits/ -o merged.apk
 java -jar uber-apk-signer.jar -a merged.apk --allowResign -o merged_signed
 ```
 
+## Android malware tradecraft (loaders, fileless DEX, persistence)
+
+### Native staging + fileless DEX loaders
+
+Some Android droppers embed a native library (`lib*.so`) that **decrypts and writes a second ELF** (e.g., `l.so`) to a temp path, loads it via JNI, and then loads the real logic as DEX **only in memory** using `dalvik.system.InMemoryDexClassLoader`. This reduces static visibility of the payload and avoids writing `classes*.dex` to disk.
+
+Practical triage points:
+- Look for native libs that `dlopen` or call `System.loadLibrary` very early, then resolve Java methods via obfuscated stack strings (e.g., XOR decoded on the stack).
+- Watch for `InMemoryDexClassLoader` in logs/strings or hooks, which indicates fileless DEX execution.
+
+Quick Frida hook to dump the in‑memory DEX buffer:
+```javascript
+Java.perform(() => {
+  const IM = Java.use('dalvik.system.InMemoryDexClassLoader');
+  IM.$init.overload('java.nio.ByteBuffer','java.lang.ClassLoader').implementation = function(buf, parent){
+    const arr = Java.array('byte', buf.array());
+    const fos = Java.use('java.io.FileOutputStream').$new("/sdcard/memdex.dex");
+    fos.write(arr); fos.close();
+    return this.$init(buf, parent);
+  };
+});
+```
+
+### Anti-analysis kill-switch
+
+Packed loaders often **self-terminate** when emulator or analysis checks fail (e.g., `CPU_ABI` validation) by calling:
+
+```java
+android.os.Process.killProcess(android.os.Process.myPid());
+```
+
+### Persistence via foreground service + MediaPlayer loop
+
+A lightweight persistence pattern is to keep a **foreground service** alive with a **pinned notification** and continuously play a near-inaudible audio loop via `MediaPlayer`. This keeps the process “active” and reduces OS inactivity kills. Look for `ForegroundService` + `MediaPlayer` usage that loops a tiny asset (often a few seconds long).
+
+### Accessibility overlay + ACTION_SET_TEXT hijacking
+
+After a user grants Accessibility, banking trojans can monitor the **foreground app**, render a realistic overlay (often WebView HTML stored as Base64), and replace transaction fields using `AccessibilityNodeInfo.ACTION_SET_TEXT`. This enables silent recipient address substitution while the victim sees a plausible UI.
+
+Minimal text replacement example:
+```java
+Bundle args = new Bundle();
+args.putCharSequence(AccessibilityNodeInfo.ACTION_ARGUMENT_SET_TEXT_CHARSEQUENCE,
+                     "ATTACKER_USDT_ADDRESS");
+node.performAction(AccessibilityNodeInfo.ACTION_SET_TEXT, args);
+```
+
+### Legitimate push infrastructure as C2 gating
+
+Instead of custom sockets, some malware uses **Firebase Cloud Messaging (FCM)** as the C2 channel. FCM messages can trigger telemetry checks (charging state, battery %, temperature, user inactivity) and **gate** actions like mining or fraud for stealth.
+
+### Encrypted native payload staging with filename‑derived keys
+
+Native payloads can be delivered as encrypted ELF blobs and decrypted with `CipherInputStream()`, using a key **derived from SHA‑1 of the downloaded filename**. Each filename/version yields a distinct key, hindering static IOC reuse.
+
 ## Jezail rooted Android pentesting toolkit (REST API + web UI)
 
 - Runs on a **rooted device** (Magisk/rootAVD) and starts an **HTTP server on tcp/8080** with a **Flutter web UI** and **REST API**.
@@ -900,5 +955,6 @@ AndroL4b is an Android security virtual machine based on ubuntu-mate includes th
 - [Build a Repeatable Android Bug Bounty Lab: Emulator vs Magisk, Burp, Frida, and Medusa](https://www.yeswehack.com/learn-bug-bounty/android-lab-mobile-hacking-tools)
 - [CoRPhone — Android in-memory JNI execution and packaging pipeline](https://github.com/0xdevil/corphone)
 - [Jezail rooted Android pentesting toolkit (REST API + Flutter UI)](https://github.com/zahidaz/jezail)
+- [BeatBanker: A dual‑mode Android Trojan](https://securelist.com/beatbanker-miner-and-banker/119121/)
 
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