What is an overlay attack?

An overlay attack is a technique where a trojan displays a fake window over a legitimate app to trick users into entering sensitive information. It typically exploits the "draw over other apps" permission.

How can I prevent mobile trojans from hijacking banking apps?

Users should download apps only from official stores, be cautious about granting sensitive permissions like Accessibility Service, and install security software. Banking apps should detect overlays and implement certificate pinning.

How do trojans intercept OTPs?

Trojans intercept OTPs by requesting SMS read permissions to capture SMS messages, or by hijacking push notifications to extract OTPs, thereby bypassing two-factor authentication.

Escalating Mobile Trojan Threats: Unveiling Real-Time Hijacking Techniques Targeting Banking Apps

5/28/2026 · 2 min

Introduction

In recent years, mobile trojan threats have escalated significantly, particularly with real-time hijacking techniques targeting banking apps. Attackers use these methods to bypass traditional security measures and steal sensitive information such as login credentials, payment passwords, and one-time passwords (OTPs). This article unveils the principles behind these techniques and explores effective defense strategies.

Overlay Attack

The overlay attack is one of the most common real-time hijacking techniques used by mobile trojans. Attackers place a fake login page or transaction confirmation window over the legitimate banking app interface. When users enter information, the data is captured directly by the trojan.

Implementation

Permission Abuse: Trojans typically request the "draw over other apps" permission (SYSTEM_ALERT_WINDOW) to create overlays.
Dynamic Injection: Using Accessibility Service, the trojan detects when a banking app is launched and immediately displays a fake interface.
Data Theft: User-entered usernames, passwords, and OTPs are recorded and sent to a remote server.

Keylogging and Screen Capture

Beyond overlay attacks, trojans also steal data through keylogging and screen capture.

Keylogging

Trojans leverage Accessibility Service to monitor user input events. Even if input fields are encrypted, they can capture keystroke sequences. Some variants record virtual keyboard click coordinates to reconstruct input content.

Screen Capture

By requesting screen recording permissions (e.g., Android's MediaProjection), trojans can record user operations in real time, including all interactions within the banking app. Attackers later analyze the video to extract sensitive information.

Session Hijacking and OTP Interception

The ultimate goal of real-time hijacking is to bypass two-factor authentication (2FA). Trojans achieve this through:

Session Cookie Theft: Exploiting WebView vulnerabilities or injecting JavaScript to steal session cookies from banking apps, allowing attackers to impersonate users for transactions.
SMS Interception: Requesting SMS read permissions to intercept OTP messages, completing transaction authorization without user knowledge.
Push Notification Hijacking: Some trojans intercept push notifications from banking apps to extract OTPs or transaction confirmation details.

Defense Strategies

To counter these advanced threats, users and financial institutions should adopt multi-layered defenses:

User Level: Download apps only from official app stores; be cautious when granting "draw over other apps" and Accessibility Service permissions; install reliable security software.
App Level: Banking apps should detect the presence of overlays and disable sensitive operations; use certificate pinning to prevent man-in-the-middle attacks; implement device fingerprinting and behavioral analysis.
Network Level: Deploy traffic encryption and anomaly detection systems to identify malicious communication patterns.

Conclusion

Real-time hijacking techniques of mobile trojans are continuously evolving, posing serious threats to banking app security. By understanding these techniques and adopting comprehensive defense strategies, risks can be effectively mitigated. Ongoing security research and user education are key to addressing this challenge.