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What Is a Keylogger? How to Detect, Test, & Defend Against Them

Keylogger - what is a keylogger blog - learn how to protect against a keylogger and malware
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What Is a Keylogger? How to Detect, Test, & Defend Against Them

Keylogger - what is a keylogger blog - learn how to protect against a keylogger and malware

What Is a Keylogger? How to Detect, Test, & Defend Against Them

Keylogger - what is a keylogger blog - learn how to protect against a keylogger and malware
  • Alex Messham
  • November 10, 2025

Why Keyloggers Still Matter in 2025


Keyloggers remain a major threat in 2025, widely used by attackers to silently capture passwords, inputs, and system activity, and by security teams to assess defense gaps during ethical red team engagements. Keyloggers can operate below traditional detection layers, enabling them to be a highly effective and dangerous credential harvesting technique. Keylogging is likely to be used to acquire credentials for new access opportunities when OS Credential Dumping efforts are not effective, and may require an adversary to intercept keystrokes on a system for a substantial period of time before credentials can be successfully captured (MITRE ATT&CK 1 & 3, 2025).

Additionally, they can serve as powerful assets in ethical security testing. Keyloggers are capable of silently capturing everything from passwords to command-line commands with little chance of detection. This guide explains what keyloggers are, how attackers use them, and most importantly, how to detect, and defend your systems against them.

What Is a Keylogger (And Why Should You Care)?


A keylogger is software or hardware that secretly records keystrokes pressed on a keyboard, or otherwise every keystroke stored in a keyboard buffer. Often used maliciously, keyloggers store or send captured data to hackers, who analyze it to steal credentials and access secure systems, usually without the victim knowing (Fortinet, 2025).

As you can see in the image below, some of the keylogger’s goals are to steal credentials, monitor commands/behaviors, and enable lateral movement.

Keylogger goals 1. steal credentials 2. monitor commands & behaviors 3. enable lateral movement

However, InfoSec professionals also employ keyloggers responsibly during penetration tests and red team operations to expose vulnerabilities. Keyloggers function at various system layers: application, operating system, kernel, and hardware — each progressively more difficult to detect. Regardless of type, their core goal is to quietly capture your keystrokes.

Types of Keyloggers


1. Software-Based Keyloggers

Software keyloggers are malicious programs that are installed directly on the target system to capture keystrokes and send or store this data for attackers. They are among the most prevalent methods attackers use to intercept user input (Fortinet, 2025).

Software-Based Keylogger types include:

  • Application-Level: Captures input via APIs and keyboard event hooks.
  • Kernel-Level: Intercepts keystrokes before system processing.
  • Form-Grabbing: Captures data from web forms prior to encryption.
  • Memory-Injecting: Injects malicious code into running processes.
  • Cross-Site Scripting (XSS): Embeds malicious JavaScript to capture typed input.


2. Hardware-Based Keyloggers

Hardware-based keyloggers are physically inserted between a keyboard and the computer (via USB or PS/2 ports). Often disguised as adapters, hardware-based keyloggers operate on the hardware level, making them hard to detect with antivirus tools. They store keystroke data locally for later attacker retrieval (SentinelOne, 2025).

Hardware-Based Keylogger Types Include:

  • Traditional: Physical devices intercepting keystrokes.
  • Wireless: Transmitting captured keystrokes remotely.
  • Acoustic: Analyzing typing sounds to reconstruct input.

Preventing unauthorized physical access is critical to mitigating hardware keylogger threats. Establish rigorous organizational BYOD policies and otherwise strong controls to restrict physical access to devices and ports (SentinelOne, 2025).

Modern Hardware-Based Keylogger Examples:

Key Croc: A smart USB keylogger developed by Hak5, equipped with penetration testing tools, remote access, and payload capabilities that trigger multi-vector keylogging attacks. It emulates trusted USB devices such as keyboards, storage, and Ethernet adapters to avoid detection and can be controlled remotely through a web interface, making it a powerful tool for cyber attackers and penetration testers alike (Hak5).

O.MG Elite Cable: A covert USB cable masquerading as a standard charger or data cable, embedding an advanced keylogging implant within. It offers features like Wi-Fi control, encrypted command-and-control communication, geo-fencing, and self-destruct mechanisms, providing attackers with stealthy control and data exfiltration options (Hak5).

By understanding these devices and their sophisticated functions, organizations can better recognize the threat landscape and reinforce physical security measures to protect sensitive input data.

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Common Ways Keyloggers (and Malware) Enter Systems

 

Defending against malware starts with knowing how threats may arrive. Keyloggers don’t magically appear; hackers use a variety of ways to sneak them onto systems.

Common ways keyloggers enter systems through phishing emails and malware

Ways Keyloggers Can Enter Systems:

  1. Phishing: Emails with malicious attachments or links.
  2. Compromised Software (Trojans): Legitimate programs altered with keyloggers.
  3. Privilege Escalation: Attackers gaining root privileges, enabling them with more privileged access to user and kernel-level software.


Understanding the ways hackers can gain access to your system can help you prioritize prevention and monitoring.

See exactly where your defenses stand and uncover hidden gaps before attackers do. Take 5 minutes to evaluate your initial security posture with our FREE RISE Foundations Assessment — your first step toward stronger, smarter protection.

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MITRE ATT&CK: Tracking Keylogger Techniques  

 

To better understand attacker behavior and strengthen defense posture, security teams often rely on the MITRE ATT&CK framework.

Key techniques associated with keyloggers include:

  • T1056.001 Input Capture: Keylogging across OS layers (MITRE ATT&CK 1, 2025).
  • Related tactics: Credential theft, privilege escalation, persistence, command-and-control.

Mapping these behaviors can help support prioritized incident response (Messham, 2025).

Effective Methods to Detect Keyloggers


Even advanced keyloggers leave clues.

Watch for:

  • Unknown or suspicious processes running from temporary or unusual directories.
  • Frequent creation or updates to obscure log files.
  • Access to device nodes like /dev/input/event* in logs.
  • Suspicious ptrace/evdev system calls.
  • Usage of suspicious Windows API Calls.
  • Suspicious changes to Windows registry or drivers.
  • Unusual outbound traffic or data exfiltration attempts.
  • Alerts from EDR tools or file integrity monitoring systems.

Use a combination of process monitoring, network analysis, and log review to find hidden keyloggers (Messham, 2025).

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Preventing and Defending Against Malware and Keylogger Attacks


Whether you’re securing desktops and servers, these foundational steps help reduce exposure to keyloggers and similar threats.

Strengthen security with these best practices:

  • Least Privilege Model: Limit user/process permissions.
  • Restrict Unauthorized Physical Access: Limit ability for unauthorized personel to access hardware.
  • Device Node Lockdown: Restrict access to /dev/input files.
  • Regular Patching & Cleanup: Update software regularly and remove unused packages.
  • Deploy EDR/MDR Tools: Enable behavior-based and memory monitoring detection and fast remediation.
  • Monitor Logs & Files: Automate alerts for suspicious changes.
  • Network Segmentation: Control endpoint connectivity and monitor unusual outbound flows.
  • Ongoing User Education: Train staff to recognize phishing and social engineering attempts.
  • Baseline Hardening: Use security benchmarks like those from the Center for Internet Security (CIS) or vendor security benchmarks.

At DataYard, we partner with teams to build tailored cloud cybersecurity strategies that fit your unique environment and risk profile. Whether you’re just starting to tighten controls or are ready for proactive threat detection, our experts are here to help simplify the process and prioritize what matters most.

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If you’d like to explore practical ways to enhance your cybersecurity defenses, feel free to reach out anytime for a no-pressure conversation about your security goals.

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Suspecting a Keylogger? Immediate Actions


If you suspect a keylogger is active on your system, act swiftly and methodically:

  • Immediately disconnect the affected device from the network to stop further data exfiltration.
  • Preserve system logs and memory dumps to support forensic investigation and understand the scope.
  • Inspect any suspicious binaries or files in a secure sandboxed environment for analysis or evidence.
  • Leverage your Next Generation Antivirus (NGAV/XDR/EDR/MDR) tools to detect lateral movement and related threats.
  • Reset all potentially compromised credentials promptly to prevent unauthorized access.

The faster you’re able to isolate and respond, the more you’ll limit damage and shorten recovery time.

Want expert guidance to help prevent this from happening again? We’re here to help.

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The Importance of Testing Keyloggers in Controlled Environments


Keyloggers are sophisticated tools that often disguise themselves as legitimate software and operate with high system privileges, making them exceedingly difficult to detect and remove (Bhardwaj & Goundar, 2020). It is crucial to regularly assess and test the effectiveness of your security controls in order to understand your ability to defend against clandestine attacks, such as keylogging, and to improve your defensive measures effectively.

OS Credential Dumping - Keylogger - What is a Keylogger - Password Guessing

How to test keyloggers:

  • Schedule a Penetration Test or Red Team engagement and include Keylogging in your desired scope.
  • Additionally, virtualization and sandboxing to replicate real attack vectors without risk to production environments.
  • Restrict test access to trained security personnel.

Final Thoughts


Understanding keyloggers — how they operate, how they infiltrate, and how to detect and defend against them — is vital in maintaining a secure system. Staying vigilant with updates, monitoring, and employee training can significantly reduce risk.

With DataYard’s managed cloud infrastructure, logging, and endpoint visibility, your environment can be centrally enforced without compromising performance.

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Take the Next Step: Assess and Secure Your Infrastructure


Review your security posture with DataYard’s RISE Foundations Assessment, a complimentary 5-10 minute evaluation offering personalized reports and actionable recommendations.

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Disclaimer
This blog post is intended for educational and informational purposes only. The techniques, tools, and references discussed, particularly those related to keylogger development, detection, or testing, are shared to improve awareness and strengthen cybersecurity defenses. Any attempt to replicate, deploy, or experiment with these tools should only be done within explicitly authorized environments for ethical testing, research, or red team operations.

Unauthorized use of keyloggers or malware violates legal and ethical standards and may result in severe consequences, including criminal charges. DataYard disclaims all responsibility for misuse of the information provided. Always consult with qualified security professionals before applying these practices to your environment.

 

References

  • November 10, 2025

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