Keyloggers are a category of spyware used by attackers to harvest credentials and sensitive data by recording everything a victim types, often operating invisibly in the background.
Why it matters
- Primary method for stealing credentials, bypassing encryption and MFA in some cases.
- Can capture data before encryption is applied (typing into HTTPS forms).
- Often deployed as part of larger malware campaigns or targeted attacks.
- Hardware keyloggers can evade all software-based detection.
Key concepts
- Software keyloggers: Malicious programs running at kernel or user level to intercept keystrokes.
- Hardware keyloggers: Physical devices installed between keyboard and computer or within keyboards.
- Form grabbers: Variant that captures form field data before HTTPS encryption.
- Screen capture: Advanced variants that also record screenshots and mouse clicks.
- Memory injection: Technique to hide keylogger code within legitimate processes.
Types of keyloggers
- API-based: Hooks Windows keyboard APIs (SetWindowsHookEx, GetAsyncKeyState).
- Kernel-level: Operates at driver level for deeper access and harder detection.
- Form grabbing: Intercepts web form submissions before encryption.
- Acoustic: Analyzes keyboard sounds to determine keystrokes (research attack).
- Hardware: USB devices, PS/2 adapters, or embedded in keyboards.
Detection techniques
- Endpoint detection and response (EDR) monitoring for hooking behavior.
- Process behavior analysis for unexpected keyboard API access.
- Physical inspection for hardware devices on workstations.
- Network traffic analysis for exfiltration patterns.
- Anti-keylogger software that encrypts keystrokes at the driver level.
Defense strategies
- Deploy robust endpoint protection with behavioral analysis.
- Use password managers with auto-fill to avoid typing credentials.
- Implement hardware security keys for phishing-resistant MFA.
- Conduct regular security awareness training about keylogger risks.
- Use virtual keyboards for highly sensitive operations.
- Physically secure workstations and audit hardware connections.
Common delivery methods
- Phishing emails with malicious attachments.
- Drive-by downloads from compromised websites.
- Bundled with pirated software or fake utilities.
- USB drop attacks with infected devices.
- Supply chain compromise of legitimate software.
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