lennart.hostettler@debian:~/

Security Engineer & Penetration Tester from Germany

I don’t hate Bill Gates because he’s a reptilian lizard injecting 5G chips from the hollow earth — I hate him because he invented Windows.

4 CVEs  —  6 Critical · 5 High · 4 Medium

4 Published · 11 Pending

3 Publications

whoami

25. Berlin & Chemnitz. I break things professionally and find vulnerabilities that have been sitting in production for years because nobody bothered to look.

I'm not going to explain who I know or how I know it. What I'll say is: I've spent years building relationships on both sides of the fence — close enough to the underground that when something moves, a campaign spins up, a zero-day changes hands, or a crew shifts targets, I hear about it. Not from threat intel feeds. Not from a vendor report. Directly, and weeks before anyone publishes a word about it. That proximity shapes how I think about threats in ways no certification ever could.

I don't do this for clout or bug bounty payouts. Broken software pisses me off. That's the whole reason.

Skills

Certifications / Courses

Experience

2023 – Present
Junior Penetration Tester & Security Engineer — SmartTECS Cyber Security
  • Conducted comprehensive penetration tests across various environments
  • Developed robust IT emergency response plans
  • Supported implementation of ISO 27001-compliant information security management systems
  • Designed and hardened Linux-based infrastructures (RHEL & Debian)
  • Integrated and monitored network detection systems (NIDS, AIDS, HIDS)
  • Threat intelligence gathering and analysis to proactively identify and mitigate emerging risks
2020 – 2023
Apprenticeship – IT Specialist for System Integration — SBE network Solutions
  • Planned, deployed, and maintained Linux-centric and hybrid infrastructures
  • Managed Samba4 Active Directory environments
  • Built containerized services with LXC and automated configurations using Puppet
  • Deployed secure proxy services via Squid
  • Implemented system monitoring and backup strategies
  • Troubleshot complex issues in Debian- and RHEL-based networks

Hobbies