Octo

What is Octo malware?

Octo, also known as Coper or ExobotCompact, is an Android banking Trojan that evolved from the Exobot malware family, first observed in 2016. Initially based on the Marcher Trojan, Exobot targeted financial institutions globally until 2018, when a lighter version, ExobotCompact, emerged.

By 2021, a new variant appeared, named Coper by some antivirus vendors, but later renamed as Octo — a rebranded and enhanced ExobotCompact. In 2024, Octo2, an even more advanced iteration, was released, driven partly by the leak of Octo’s source code. The Malware-as-a-Service (MaaS) model makes Octo accessible to even novice cybercriminals.

Lineage:

• Exobot, an Android banking trojan that went inactive, and its source code leaked.
• ExobotCompact, a more compact version with no dependency on older Android APIs.
• Octo, enhanced version with powerful remote access and evasion features.
• Coper is sometimes considered a separate but related strain, circulating in Latin America, sharing infrastructure/code.

Octo’s Distribution

The malware targets Android devices through social engineering and malicious app distribution:

• Fake Apps and Droppers: Octo disguises itself as legitimate apps like Google Chrome, NordVPN, or banking apps, often using a dropper service called Zombinder to bundle with legitimate APKs. These are typically distributed via third-party app stores, malicious websites, or phishing campaigns, though some droppers.
• SMS Phishing (Smishing): Messages with malicious links trick users into downloading fake apps posing as WhatsApp, Netflix, or banking services. This functionality is similar to that of Salvador Stealer, another Android banking trojan.
• Social Engineering: Campaigns often impersonate trusted brands or simulate urgent software updates. Regional targeting, such as fake Bancolombia apps for Colombian users, enhances credibility.

Once installed, Octo prompts users to enable Accessibility Services and give out Device Admin privileges, granting extensive control over the device, and enhances remote access stability.

Its communications with C2 servers include dynamic configurations to target specific apps (e.g., to block push notifications from banking apps).

Octo’s Key Operation Vectors

• Keylogging: to capture credentials, PINs, and lock patterns. Data is temporarily stored in the device’s data directory before deletion to avoid detection.
• Overlay Attacks: the trojan displays fake login screens or overlays mimicking banking apps to steal credentials and card details. Overlays adapt dynamically to the active app, increasing deception.
• SMS and Notification Interception: Intercepts messages and push notifications, enabling attackers to bypass two-factor authentication (2FA).
• Remote Access (VNC): Uses Android’s MediaProjection for near-real-time screen streaming (1 screenshot per second. Sends live feed to C2, allowing attackers to see everything that happens on the device.
• Device Takeover: Can simulate clicks and actions in real-time.
• Ransomware-Like Locking: Some variants (like Coper) can lock screens and demand ransom.

Why Octo Is Especially Dangerous

• Full Remote Control of Mobile Devices.
• Live Monitoring and Fraud: Attackers perform fraud while victims are active, bypassing behavioral fraud detection.
• Two-Factor Authentication Bypass: Through SMS or code-grabbing overlays.
• Modular Structure: Can load updated components from C2 without user knowing.
• Enterprise Risk: Can be used as an entry point into corporate networks via compromised employee devices (BYOD); targets banking customers and employees.

Octo’s Execution Process and Evasion Techniques

ANY.RUN’s Interactive Sandbox supports the analysis of APK files and enables the research of Android malware. Let us observe the behavior of an Octo sample where the malware is disguised as Google Chrome browser.

View Octo analysis session in the Sandbox

Once installed, Octo — also known as Coper or ExobotCompact — connects to its command and control (C2) server, potentially using a domain generation algorithm (DGA) to maintain resilient, encrypted communication. In our case, the address was toplamakampiyolculukhazirlik[.]xyz, visible in the DNS requests tab, though unresolved. The C2 provides configuration files and commands specifying which apps to target and what actions to take. In this task, the C2 was already offline.

Octo abuses Android’s Accessibility Service and MediaProjection APIs to gain full remote control, enabling real-time screen streaming, simulated taps, gestures, clipboard access, and text input. To stay hidden, it can display a black screen, dim brightness to zero, and disable notifications.

The malware supports keylogging, SMS and notification interception, blocking app alerts, screen locking/unlocking, muting sound, launching apps, and sending SMS. Attackers use AES-encrypted, Base64-encoded commands to control these features and perform on-device fraud—initiating and confirming transactions without triggering alarms.

Octo mobile trojan analysis in ANY.RUN's Interactive Sandbox

Octo can also inject fake overlays to steal credentials and uninstall competing or security apps to maintain persistence and avoid detection.

This malware employs advanced methods to avoid detection. It requires no root access using Accessibility Services for control. Its small, modular codebase demonstrates a lightweight footprint helping to avoid detection by traditional antiviruses. Besides, obfuscation is applied, along with multi-layered code encryption, dynamic loading of malicious libraries. Continuous updates by developers and forks from the 2024 source code leak keep Octo ahead of traditional detection methods.

What are the best-known Octo attacks?

While many campaigns are not publicly attributed due to the nature of mobile malware distribution, several have been documented by security vendors and researchers.

Gathering Threat Intelligence on Octo malware

Octo can be detected by such indicators as C2 domains, IPs, and unusual DNS traffic. Among the behavioral indicators, analysts should pay attention to background services that relaunch on boot, the use of Accessibility APIs, and unexpected overlays over banking apps. Its APK signatures include package names often mimicking known apps and typical permissions requests, like SYSTEM_ALERT_WINDOW, BIND_ACCESSIBILITY_SERVICE.

To start gathering actionable data via ANY.RUN's Threat Intelligence Lookup, search for the malware name and its aliases:

threatName:"octo" OR threatName:"exobot*"

Add all of the Octo’s names to a single search request

Select and view analysis sessions to collect IOCs, IOBs, view processes, and study the malware’s TTPs to set up detection and response system, to develop prevention and mitigation strategies.

View malicious processes in detail

Conclusion

Octo malware (ExobotCompact / Coper) is one of the most advanced mobile threats in circulation, particularly dangerous because it provides real-time remote access and can bypass many layers of authentication and fraud detection. While it mainly targets banking users, its modularity and stealth make it a viable tool for cybercrime groups and potential APT-style attacks against enterprises. Countering Octo demands robust threat intelligence, proactive user education, and strict device security practices.

Start with 50 requests in TI Lookup to collect IOCs on the evolving Android malware