What is a Keylogger? Definition, Detection & Protection

Keyloggers are one of the most covert tools used by cybercriminals to capture everything a user types - passwords, emails, credit card numbers, and more - without them even knowing. These malicious tools can silently run in the background, collecting sensitive data and transmitting it to unauthorized third parties.

Whether introduced through phishing emails, infected downloads, or physical devices, keyloggers pose a serious risk to both individuals and organizations. Their ability to remain undetected makes them particularly dangerous, demanding proactive detection and strong protection measures.

In this blog, we’ll cover what keyloggers are, the different types, how they operate, effective ways to detect them, and proven strategies to protect your systems.

What are Keyloggers?

Keyloggers are designed to monitor and capture every keystroke entered on a keyboard, turning everyday computer use into a data leak without any visible signs. Their primary purpose is to collect sensitive information—often for malicious use—by logging data in real-time.

These tools can vary widely in form and function. Some are embedded within malware and silently installed through compromised software or infected websites. Others come as physical devices that attach discreetly to keyboards or USB ports.

While some keyloggers have legitimate uses - like monitoring employee productivity or parental controls - their misuse in cybercrime has made them a serious cybersecurity concern. Understanding how they operate is the first step in effectively defending against them.

Types of Keyloggers

Keyloggers fall into two main categories based on how they operate: software-based and hardware-based. Understanding the difference is critical for implementing the right detection and protection measures.

Software-Based Keyloggers

Software-based keyloggers are malicious programs installed on a device without the user’s consent. They often arrive through phishing emails, infected attachments, or downloads from untrusted websites. Once installed, they run silently in the background, capturing every keystroke and often transmitting this data to a remote server.

These keyloggers can integrate with the operating system, web browsers, or even specific applications, making them harder to detect with traditional antivirus tools. Their ability to remain hidden and scale across multiple systems makes them a popular choice for cybercriminals.

Hardware-Based Keyloggers

Hardware-based keyloggers are physical devices that are manually connected between a keyboard and a computer or inserted inside a USB port. They don’t require software installation, which makes them particularly difficult to detect through digital security tools.

Because they require physical access, hardware keyloggers are commonly used in targeted attacks, such as insider threats or espionage campaigns. Once connected, they begin logging keystrokes as soon as the machine is used, often storing the data locally for later retrieval.

How Do Keyloggers Work?

Keyloggers function by intercepting and recording the keys you type on your keyboard—without alerting the user. Once active, they collect sensitive data like passwords, credit card details, and private messages, then transmit this information to attackers.

There are two primary methods keyloggers use to capture data:

• Software-Based Operation: These keyloggers hook into the operating system or browser to monitor keyboard activity. Some log every keystroke, while others only trigger when specific websites or applications are opened.
• Kernel-Level Logging: More advanced keyloggers operate at the system’s kernel level, giving them deep access to input data and allowing them to bypass standard security software.

In both cases, the logged data is either stored locally on the device or sent to a remote server controlled by the attacker. This makes keyloggers especially dangerous - they operate silently and can remain undetected for extended periods.

Common Attack Vectors Used for Infecting Keyloggers

Keyloggers infect systems by taking advantage of everyday user actions and weak security practices. They often enter through phishing emails, malicious downloads, or unpatched software. Knowing these specific entry points helps organizations block keyloggers before they can cause harm. Let’s delve into the most common methods attackers use to deploy keyloggers.

Phishing Emails

Phishing remains the most frequent delivery method for keyloggers. Cybercriminals send deceptive emails that urge users to click on malicious links or open infected attachments. These emails often appear legitimate, impersonating trusted brands or colleagues. Once clicked, the keylogger installs silently and begins logging keystrokes without detection.

Malicious Downloads

Downloading pirated software, unofficial plugins, or cracked tools from unreliable sources can lead to automatic keylogger installation. These programs often bundle malware that runs in the background without the user’s awareness. Even seemingly harmless utilities or games can be weaponized. Without a robust endpoint protection tool, users may never realize they've been compromised.

Drive-by Downloads

Just visiting a compromised or malicious website can trigger a download. Known as drive-by attacks, these exploit vulnerabilities in browsers or plugins to silently install keyloggers without any user action. Attackers typically leverage outdated Flash or Java plugins for this method. Users don't need to click anything—the infection occurs automatically.

Exploiting Software Vulnerabilities

Outdated operating systems and applications are prime targets for exploitation. Hackers take advantage of known flaws to install keyloggers directly into the system—no clicks or downloads required. These attacks often bypass antivirus tools by exploiting zero-day vulnerabilities. Regular patching is critical to close these entry points.

Removable Media Attacks

USB drives and other external devices are often used in targeted attacks. A keylogger embedded in the device can auto-install as soon as it's connected to a computer, bypassing many standard defenses. These attacks are common in physical environments like libraries or shared workspaces. Even charging a phone from an unknown USB port can be risky.

By identifying these attack methods, organizations can take preemptive action through updated software, secure browsing practices, and ongoing Security Awareness Training.

Real-Life Incidents Related to Keyloggers

Below are real-world incidents that demonstrate how keyloggers have been used in cyberattacks to silently capture keystrokes, steal sensitive information, and compromise organizations across various sectors.

These keylogger incident examples highlight the importance of proactive monitoring, endpoint protection, and user training in defending against keylogger threats.

Zeus (2007)

A notorious banking Trojan used by organized cybercriminals, affecting financial institutions and individuals globally.

Caused hundreds of millions in damage. Resulted in international collaboration, arrests, and convictions, highlighting global cybersecurity efforts. (Source)

FinFisher (2011)

Employed by authoritarian governments and cybercriminals to target political dissidents, journalists, and users globally.

Sparked global outcry and led to tighter controls on software sales, raising ethical questions about surveillance. (Source)

Project Sauron (2015)

A state-sponsored keylogger that targeted governments and large corporations in Russia, Iran, and Rwanda.

Led to international cybersecurity countermeasures and enhanced defenses, reflecting state-level cyber threats.(Source)

HawkEye Reborn (2019)

Used by well-organized cybercriminals to target individuals and businesses globally, stealing email credentials and banking details.

Responses included new antivirus definitions and legal pursuits, showing ongoing efforts to combat keylogger threats. (Source)

Agent Tesla Keylogger Attack (March 2024)

In March 2024, attackers sent out fake bank emails with a dangerous file attached. When someone opened the file, it secretly installed a keylogger called Agent Tesla on their computer.

The keylogger was hidden using special tricks to avoid antivirus scans and didn’t leave any clear signs of infection. It recorded everything the user typed and sent the stolen data through a real email account from a company in Turkey.

This made the attack hard to detect and trace. The case shows how easy it is to fall for realistic-looking emails—and why strong phishing protection and employee training are so important. (Source)

SnakeKeylogger Malware (August 2024)

Hundreds of zero-day detection hits were reported for SnakeKeylogger (aka KrakenKeylogger), targeting Windows systems. Spread through phishing campaigns using malicious Office documents or PDFs with PowerShell downloaders, it logs keystrokes, steals credentials, takes screenshots, and exfiltrates data via FTP, SMTP, or Telegram.

Demonstrated the effectiveness of advanced keylogging malware in evading detection, with significant detection efforts by Fortinet and others. (Source)

MS Exchange Server Flaws Exploited to Deploy Keylogger (May 2024, Reported in 2025)

Attackers exploited ProxyShell vulnerabilities (CVE-2021-34473, CVE-2021-34523, CVE-2021-31207) in Microsoft Exchange Server to deploy a keylogger, targeting over 30 victims across Africa, the Middle East, Russia, U.A.E., Kuwait, Oman, Niger, Nigeria, Ethiopia, Mauritius, Jordan, and Lebanon.

Showcased the continued exploitation of older vulnerabilities for deploying keyloggers, affecting critical infrastructure and organizations. (Source)

Hiding Malware in Images to Deploy VIP Keylogger (January 2025)

A campaign was discovered where attackers hid malware within image files to deploy VIP Keylogger and 0bj3ctivity Stealer, leveraging CVE-2017-11882 for execution.

Highlighted creative methods to evade detection, with the keylogger used for stealing sensitive information. (Source)

New Snake Keylogger Variant (February 2025)

A new variant of Snake Keylogger was reported, utilizing AutoIt scripting, with over 280 million blocked attempts. Primarily distributed through phishing campaigns targeting users in China, Turkey, Indonesia, Taiwan, and Spain, it used SMTP and Telegram bots for data exfiltration.

Demonstrated the evolving nature of keylogger threats, with significant blocking efforts indicating widespread distribution. (Source)

How to Detect a Keylogger

Detecting a keylogger can be challenging because they are designed to remain hidden. The table below outlines key warning signs and methods that help identify their presence:

For organizations, combining endpoint protection with continuous phishing simulations and security awareness training can improve early detection and reduce risks.

How to Protect Against Keyloggers

Stopping keyloggers before they cause harm requires a mix of smart user habits and strong technical defenses. Here are the most effective ways to protect yourself and your organization:

• Use trusted security software: Install and regularly update antivirus and anti-malware tools that can detect and block keylogger activity.
• Enable multi-factor authentication (MFA): Even if a keylogger captures your password, MFA adds an extra layer of protection that can stop unauthorized access.
• Avoid risky clicks and downloads: Be cautious with links, email attachments, and free software—these are common ways keyloggers get in.
• Use keystroke encryption tools: These tools scramble what you type, making it unreadable to keyloggers even if they are active on your device.
• Train your team: Ongoing Security Awareness Training helps users recognize phishing attempts and other threats that can lead to keylogger infections.

Combining these practices with proactive tools like a Phishing Simulation Tool will greatly reduce your exposure to keylogger threats.

How Keepnet Helps Mitigate Keylogger Risks

Keepnet reduces the risk of keylogger infections by targeting their most common entry point—human behavior. Its platform combines automation, AI, and tailored education to proactively defend against phishing, social engineering, and insider threats. Here’s how:

• Cyber Security Awareness Training: Delivers customized training based on employee roles to improve awareness of specific threats like phishing emails carrying keyloggers.
• AI-Powered Phishing Simulator: Launches smart, real-world phishing campaigns that teach users how to spot and avoid fake emails that often deliver keyloggers.
• Incident Response: Accelerates threat analysis and response - up to 48.6 times faster - to contain email-based attacks before they cause serious harm.

Keepnet helps organizations build a strong security culture by eliminating employee-driven threats through adaptive simulations and training.

Explore the full capabilities of the Keepnet Human Risk Management Platform to proactively reduce keylogger risks and strengthen your organization’s overall cyber resilience.