Yannick Sautter

LeetCode Hack The Box SoundCloud
Hey, thanks for stopping by!

My name is Yannick Sautter.
I lead the development of groupios, a secure multi-tenant e-mail and groupware platform, at step3IT. Besides building the product, I take care of the infrastructure it runs on, how we monitor and secure it, and the development process around it.

During my studies I focused on Cybersecurity and Machine Learning. Some of that research has been published at ARES and ESORICS. I also love tinkering with software, especially to improve my own Linux workflow. Since data privacy matters a lot to me, I also run my own LLMs locally for anything private.

Take a look at my resumé, or check the timeline below for a quick overview.

Timeline

  • 2014
    Abitur, Max-Planck-Gymnasium Saarlouis
    I finished school with computer science as one of my exam subjects. I could choose it from 10th grade on.
  • 2015
    Working Holiday, New Zealand
    After school I spent nine months in New Zealand on a "Working Holiday" visa. On the way back I stayed two months in South-East Asia.
  • 2016
    Technical Support, Arvato
    Between my travels and my first semester I worked for Arvato, a service provider for the German internet and telecommunications provider O2.
  • 2019
    Software Engineer, Freelancer
    During my bachelor studies I started working as a freelance software engineer, building management interfaces for firewall systems.
  • 2020
    Computer Science Bachelor, Universität des Saarlandes
    My bachelor thesis was "Backdoor attacks against Generative Models and Autoencoders". The results are on arXiv.
  • 2020
    Software Engineer, Tuxguard GmbH
    I built features for firewalls, antivirus endpoints and mail transfer agents. I also designed and implemented the software licensing mechanism for our products, including both the license server and the client. From 2021 on, I built the internal IT infrastructure, which still runs and grows today.
  • 2024
    Computer Science Master, RWTH Aachen
    My master studies focused on Cybersecurity and Machine Learning. My thesis was "Internationalizing DGA Detection".
  • 2024 - 2025
    Lead Developer, Tuxguard GmbH
    I led the development of groupios, a secure multi-tenant groupware solution, and moved it to a scalable manager/worker architecture.
  • 2025 - Current
    Lead Developer, step3IT GmbH
    After step3IT acquired groupios, I continued to lead its development there. We are currently turning it into a hosted SaaS offering.
  • 2026
    Security & Compliance, step3IT GmbH
    I set up a SIEM and SBOM-based vulnerability tracking for the whole Docker fleet, helped implement the ISMS (ISO 27001 & ISO 9001), and took responsibility for the software development process.
  • 2026
    Papers at ARES & ESORICS
    Both papers were the result of the research in my master thesis on DGA detection. They were published at ARES 2026 in Linköping and ESORICS 2026 in Rome.

Expertise

What I actually do day to day, not every tool I have touched once.

Secure E-Mail & Groupware

I lead groupios, a multi-tenant mail gateway and groupware platform, on-prem and SaaS.

  • Haraka
  • Rspamd
  • Keycloak
  • SPF/DKIM/DMARC
  • DANE
  • Kopano
  • CipherMail
  • OpenLDAP

Security Operations

SIEM and SBOM-based vulnerability tracking for the whole fleet, CVE triage and incident response.

  • Wazuh
  • Dependency-Track
  • CycloneDX SBOM
  • fail2ban
  • OPNsense

Process & Compliance

I own the development process: templates, branching, mandatory reviews, and CI/CD that enforces it.

  • ISO 27001
  • ISO 9001
  • GitLab CI/CD
  • Release Management
  • KPIs
  • Code Review

Infrastructure

The self-hosted company IT at Tuxguard and step3IT: Git, registry, chat, files, SSO and monitoring.

  • Linux
  • Docker
  • Nginx
  • GitLab
  • Prometheus
  • Grafana
  • Matrix/Element
  • Nextcloud
  • Tailscale

Software Engineering

Backend APIs, web UIs, desktop clients and licensing systems, mostly in Python and Go.

  • Python
  • Go
  • TypeScript
  • Django
  • React
  • C#
  • FastAPI
  • PostgreSQL
  • Redis
  • RabbitMQ

ML for Security

Research on adversarial ML: backdoors in generative models and DGA classifiers that IDNs can evade.

  • PyTorch
  • Transformers
  • DGA Detection
  • Adversarial ML
  • LaTeX

Languages: German (native) · English · French · Spanish

Side Projects

Things I build in my spare time. Most of them run in production on my own server or in my home lab.

My Hyprland desktop with the Quickshell bar, a dashboard panel with calendar, weather and tasks, Neovim and btop
Daily driver

Hyprland Rice & Desktop Shell

My own desktop shell on top of Hyprland, about 7,000 lines of QML.

  • Status bar with vi-style keyboard navigation, quick settings and notifications
  • Launcher with calculator, emoji and clipboard modes, plus an AI chat overlay
  • Colours follow the current wallpaper live
  • Quickshell
  • QML
  • Hyprland
  • Wayland
  • Qt
  • Linux
Daily driver

Private Local AI

Open-weight LLMs on my own GPU box. Private prompts and documents never leave my network.

  • The workstation sleeps when idle and wakes on the first request
  • llama-swap switches between Gemma, Qwen and co. on demand
  • Self-hosted agents with private web search and scraping
  • llama.cpp
  • llama-swap
  • Hermes Agent
  • SearXNG
  • Firecrawl
  • Wake-on-LAN
The music school app on two phones, week view and invoice, in front of a generated PDF invoice (demo data)
In production

Music School Management

A mobile-first PWA that replaced a music school's Excel sheets.

  • About a dozen teachers record lessons on their phones
  • Monthly invoice as a PDF in one tap
  • Versioned price lists and invoice approval for admins
  • Django Ninja
  • React
  • TypeScript
  • PostgreSQL
  • PWA
  • Docker
nora-dreyer.de on desktop and phone
Live

Piano Teacher Website

A one-pager for a piano teacher in Köln, with a three.js piano scene.

  • Students request trial lessons right on the page
  • Admin UI for the teacher to manage her students
  • React
  • three.js
  • Express
  • PostgreSQL
  • Docker
nora-dreyer.de
horstdreyer.de on desktop and phone
Live

Artist Portfolio Website

A gallery of a painter's oil and acrylic paintings, watercolours and drawings.

  • Password-protected admin panel
  • The artist uploads and manages the gallery himself
  • PHP
  • Bootstrap
  • JavaScript
  • Apache
  • Docker
horstdreyer.de
Running 24/7

Self-Hosted Server & Home Lab

One VPS is the only way in. Everything else lives at home, behind WireGuard.

Swipe to see the whole diagram →

Self-hosted setup All public traffic enters through one VPS. An SNI router sends mail to Stalwart and everything else to nginx-proxy. nginx-proxy serves local containers or forwards through a Tailscale gateway over WireGuard to the home lab, where every app runs with its own Tailscale sidecar. Immich photos are backed up nightly with restic to a separate disk. Internet Browsers Phone apps Mail clients photo backup web traffic mail WireGuard mx.sautter.dev VPS · the only public entry point fail2ban · own filters · regular log reviews sniproxy routes :443 by TLS SNI, without decrypting Stalwart mail · SMTP IMAP JMAP nginx-proxy TLS · Let's Encrypt Local apps sautter.dev Webmail Headscale Pi-hole · DoH Dawarich Client websites Tailscale gateway nginx inside a tailnet node Own control plane: Headscale hands out the keys, no account at tailscale.com. Traffic flows directly over WireGuard. Home lab reachable only through the tailnet Private AI · not public wake-on-llama proxy → Wake-on-LAN GPU workstation sleeps until needed llama.cpp · Hermes agents · SearXNG Apps, each with its own Tailscale sidecar Nextcloud Matrix Paperless Mealie Actual Budget Donetick Immich ntfy restic · every night at 03:00 Immich DB dump + photos + archive → separate backup disk keeps 7 daily · 4 weekly · 12 monthly integrity check after every run SNI mx.sautter.dev all other hosts WireGuard 1 2 3 4 5 6

How a photo from my phone gets backed up

  1. My phone uploads it to media.sautter.dev.
  2. sniproxy routes by SNI. Mail goes straight to Stalwart.
  3. nginx-proxy terminates TLS with Let's Encrypt.
  4. The Tailscale gateway forwards it over WireGuard.
  5. Immich runs at home as its own tailnet node.
  6. restic backs it up every night and verifies the repository.
  • Headscale is my own Tailscale control plane, with no third-party account
  • Every home app gets its own Tailscale sidecar
  • fail2ban with my own filters; I review the logs for attacks that slipped through
  • Pi-hole with DNS-over-HTTPS for all my devices
Experiment

SpamBERT

Fine-tuning EuroBERT to catch spam and phishing in European languages, not just English.

  • Binary and multiclass classifiers
  • A pipeline that generates and machine-translates training data
  • PyTorch
  • Transformers
  • EuroBERT
  • Hugging Face Datasets
Running

Automation & Bots

Small tools that take care of everyday chores for me.

Camera archiver

A Home Assistant app moves the motion clips from my cameras' SD cards to my NAS.

Home Assistant · Python

Appointment watcher

Watches the Köln city office calendar and sends a Telegram alert when an earlier slot opens.

Playwright · Telegram API

Marketplace watcher

Scrapes new classified ads every day; an LLM checks the photos for what I'm looking for.

Firecrawl · LLMs

Publications

Photography

Sun rising over the sand dunes of the Sahara
Sunrise over the SaharaMorocco
Gold mosaic arch of the mihrab in the Mezquita of Córdoba
Mihrab of the MezquitaCórdoba, Spain
The Alhambra in front of the snow-capped Sierra Nevada
Alhambra & Sierra NevadaGranada, Spain
The Milky Way above beds set up outside in a desert camp
Milky Way over the desert campSahara, Morocco
Red and white striped roses
Roses
A saddled camel lying on the beach in front of the surf
Resting camelAtlantic coast, Morocco
A lighthouse on the horizon behind sea mist and waves
Lighthouse in the sea mist
A small black bird singing on a wooden fence in front of a sand dune
Desert birdSahara, Morocco
The sun setting over the water, framed by palm trees
Sunset between palms
Sun rays breaking through clouds over a bay at dusk
Evening on the coastCantabria, Spain
A green parakeet sitting on a branch
Parakeet
The sun setting behind desert grass in an orange sky
Sunset in the desertSahara, Morocco
A dam and reservoir between steep mountain slopes
Reservoir in the mountainsSierra Nevada, Spain
Plants growing on old roof tiles above the city of Granada
Rooftops of GranadaGranada, Spain
The Alhambra in the evening light, seen through trees
Alhambra at duskGranada, Spain
Evening light breaking through clouds over a mountain range
Light over the mountains

Yannick Sautter

Software Engineer

Education

  • Master of Science
    Computer Science
    RWTH Aachen
    Templergraben 55, 52056 Aachen
    2020 - 2024
  • Bachelor of Science
    Computer Science
    Universität des Saarlandes
    Campus, 66123 Saarbrücken
    2016 - 2020

Skills

Programming

  • Python
  • JavaScript / TypeScript
  • HTML/CSS
  • Java
  • Bash
  • PHP
  • C
  • C#
  • Go
  • SQL
  • TCL
  • Flutter
  • Dart

Frameworks

  • PyTorch
  • Transformers
  • Django
  • FastAPI
  • Express
  • React
  • Bootstrap
  • Haraka
  • .NET

Tools

  • Git
  • Docker
  • Nginx
  • Apache
  • Keycloak
  • OpenLDAP
  • Redis
  • RabbitMQ
  • WiX Installer
  • GitLab CI/CD
  • Wazuh SIEM
  • Dependency-Track

Operating Systems

  • Linux (Arch, AlmaLinux, Ubuntu)
  • BSD (FreeBSD)
  • Windows

Languages

  • German
  • English
  • French
  • Spanish

Work Experience

  • Lead Developer groupios
    step3IT GmbH
    2025 - current
    Remote
    • Leading development of the on-premises and SaaS multi-tenant e-mail server, gateway and groupware groupios.
    • Building groupios as a hosted SaaS offering (in progress).
    • Responsible for the software development process, and implemented the CI/CD that enforces it (dev/qa/rc branching, reviews, release promotion, secret scanning).
    • Set up a Wazuh SIEM, SBOM generation and Dependency-Track vulnerability tracking with KPIs for all Docker services.
    • Helped implement the ISMS according to ISO 27001 and ISO 9001.
    • Continuing to run and grow the internal IT infrastructure, which has been migrated several times since 2021.
  • Lead Developer groupios
    Tuxguard GmbH
    2024 - 2025
    Remote
    • Led development of the on-premises multi-tenant e-mail server and gateway.
    • Redesigned the platform into a horizontally scalable manager/worker architecture.
  • Software Engineer
    Tuxguard GmbH
    2020 - 2024
    Remote
    • Designed and implemented the software licensing mechanism (license server and client) and a highly distributable license infrastructure for antivirus endpoints.
    • Developed and implemented on-premises installable management server for antivirus endpoints.
    • Developed and implemented plugins for OPNsense.
    • Technical Support for the products
    • Built the internal IT infrastructure from 2021 on (GitLab, registry, Matrix/Element, Nextcloud, ntfy, SSO, password management, monitoring, custom services)
    • Administrative responsibility of DNS, Firewall and Networking infrastructure
    • Developed and implemented on-premises installable multitenancy e-mail server and gateway server
    • Developed and implemented webfilter client for Windows
    • Giving training courses for the developed software
    • Writing and maintaining manuals for the products
    • Maintaining license infrastructure
    • Setting up CI/CD pipelines in GitLab
  • Software Engineer
    Freelancer
    2019 - 2020
    Remote
    • Revamped the user interface of a legacy firewall system to enhance usability and functionality.
    • Designed and implemented a multitenancy firewall management interface to support multiple users and streamline operations.
  • Technical Support
    GiGroup/Arvato
    2015 - 2016
    Eiweiler
    • Provided technical support in a call center, assisting clients with home network and internet connectivity issues. Utilized communication skills and technical expertise to deliver effective solutions and enhance customer satisfaction.
  • Working Holiday
    Kerimoore Orchards LTD,
    Karioi Limited,
    J2 Contracting,
    New J R Contracting
    2014 - 2015
    New Zealand
    • Engaged in the harvesting and sorting of oranges to ensure quality standards
    • Participated in grape harvesting, focusing on efficiency and precision
    • Managed kiwi orchard tasks, including planting, pruning, and general garden maintenance
  • Internship
    Net-Compass
    2012
    Lebach
    • Assisted in populating and managing data within the CMS to ensure accuracy and completeness.

Publications

  • A. Drichel, Y. Sautter, U. Meyer. Internationalizing DGA Detection. ESORICS 2026.
  • A. Drichel, Y. Sautter, U. Meyer. DomainBERT: Transformer-based Domain Generation Algorithm Detection. ARES 2026.
  • A. Salem, Y. Sautter, M. Backes, M. Humbert, Y. Zhang. BAAAN: Backdoor Attacks Against Autoencoder and GAN-Based Machine Learning Models. arXiv 2020.
© 2026 Yannick Sautter · Impressum · Datenschutz