David Lionis

Cybersecurity and artificial intelligence

I specialise in securing web applications and AI LLM projects. Drawing on both offensive and defensive experience, I also advise you on your overall security posture, in Luxembourg and across Europe.

Portfolio

What I do

About
  • Web and application security

    Web and API penetration testing, code reviews and support for development teams towards a secure development lifecycle. I find the weaknesses before attackers do, then help you fix them.

    • Pentest web & API
    • Code review
    • OWASP Top 10
    • Secure coding
  • AI security

    Red teaming of LLM-based applications: prompt injection, guardrail bypass and data leakage. Tool-driven, reproducible testing with concrete recommendations.

    • LLM red teaming
    • OWASP LLM Top 10
    • Garak
    • PyRIT
  • Cybersecurity advisory and expertise

    I help you choose the right security solutions, then deploy and configure them: SIEM, EDR, multi-factor authentication, web filtering and vulnerability management. Operational security, tailored to your environment.

    • SIEM
    • EDR
    • MFA
    • Vulnerability management

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