Fabian Faessler: The Hacker Behind LiveOverflow

For a lot of people who learned hacking in the past decade, the first teacher was a YouTube channel called LiveOverflow: a calm German voice explaining memory corruption over a scrolling terminal.

The man behind it is Fabian Faessler, a Berlin hacker who started filming his own learning process in 2015 and never quite stopped. His channel has close to a million subscribers and 67 million views, one video alone has been watched 3.4 million times, and his capture-the-flag team was once ranked sixth in the world.

He also, by his own account, ran out of videos to make. What he did next, and why he went quiet for nearly three years, is the more interesting story.

Fabian Faessler at a Glance

• Faessler created the LiveOverflow channel in March 2015 and posted its introduction that December; its bio still calls him "just a wannabe hacker."
• His binary exploitation series and "The Secret step-by-step Guide to learn Hacking," watched 3.4 million times, made the channel a popular starting point for new hackers.
• He's played capture-the-flag with ALLES!, a German team that ranked sixth in the world and first in Germany in 2020.
• In January 2019 he incorporated Security Flag GmbH in Berlin to produce IT teaching material, run events and sell merchandise.
• In April 2021, after six years and more than 300 videos, he admitted on camera that he'd "made every video I ever wanted to make."
• In April 2023 he and hardware hacker Thomas Roth, known as stacksmashing, founded Hextree GmbH, a cybersecurity learning platform built as an explorable map of micro-courses.
• PortSwigger put him on the expert panel that picked the top 10 web hacking techniques of 2024.
• After being "pretty inactive the past 2-3 years," he returned in August 2026 with a 40-minute video on his life, AI and the channel's future.

The Life of Fabian Faessler

Bin 0x00

On December 14, 2015, LiveOverflow posted a three-minute clip titled "LiveOverflow Channel Introduction and Backstory." Its chapters read like a syllabus for the years that followed: why he wanted to learn hacking, how he went from programming to his first capture-the-flag contest, and why he'd decided to start filming.

The channel description still sets the tone: "just a wannabe hacker... making videos about various IT security topics and participating in hacking competitions."

The format was simple. Instead of a polished lecture, Faessler worked through a problem on screen and explained what he was thinking as he went.

Learning in Public

The early playlists were a self-taught curriculum. The binary exploitation and memory corruption series walked viewers from how a program lays out memory to writing their first exploit. Later came hardware security research and a series on game hacking, built around Pwn Adventure 3, a game built to be hacked.

The audience grew with the ambition. "The Secret step-by-step Guide to learn Hacking" has 3.4 million views, and the channel passed 900,000 subscribers.

He also kept competing. On the scoreboards of CTFtime he appears among the members of ALLES!, a German academic team that finished first in Germany in 2019 and 2020 and sixth in the world in 2020.

Security Flag GmbH

By 2019 the channel was a business. That January, Faessler registered Security Flag GmbH with the Berlin commercial court, with €25,000 in capital and a stated purpose of developing and selling IT teaching media, running events and selling merchandise.

He's been unusually open about the money. A 2019 video broke down the channel's finances, and a follow-up in May 2023 gave what he called a transparent look at revenue, expenses, sponsorships and Patreon income.

Supporters could pay per video on Patreon or per month through YouTube memberships. The company's imprint lists its CEO plainly: Fabian Faessler.

Every Video He Ever Wanted to Make

In April 2021, six years and more than 300 videos in, Faessler posted an unusually candid update. "I'm running out of ideas for videos," he wrote. "I made every video I ever wanted to make... At least that's how I feel."

Everything he knew, he felt, he'd already shared. It was the kind of admission creators rarely make. In hindsight, it was the first sign that the channel wouldn't stay his only project.

Hextree

The answer was a school. On April 17, 2023, Faessler and Thomas Roth, the hardware hacker behind the stacksmashing channel, registered Hextree GmbH in Berlin to build a cybersecurity learning platform and sell the hardware its courses need.

Hextree presents its courses as an explorable map rather than a linear track, broken into short micro-lessons with hands-on labs that are "real websites that you can test to the max." In his May 2023 financials video, Faessler explained that he started Hextree as another way to fund the channel.

The platform also spawned a podcast. Episode 1 of the Hextree Podcast sat down with Kristoffer Blasiak of Google's mobile bug bounty program.

The Judge

By 2025 Faessler was being asked to rank other people's research. When PortSwigger assembled its expert panel to choose the top 10 web hacking techniques of 2024, the judges were Nicolas Grégoire, Soroush Dalili, STÖK, James Kettle and "Fabian (LiveOverflow)."

His notes read like his videos. One deep dive into HTML sanitizer bypasses was "an absolute joy to read," and of Orange Tsai's Apache research he wrote that the author "treats Apache httpd like a web CTF challenge!"

Three Years Away

Then the uploads mostly stopped. On August 23, 2026, Faessler returned with "My Life, AI and the Future of LiveOverflow," opening with an admission: "I have been pretty inactive the past 2-3 years and a lot has happened."

The chapter list tells the shape of it: a 2023 to 2024 break spent building Hextree's Android courses, the release of ChatGPT, a 2024 break and drained savings, DeepSeek and what he calls his AI "eureka!" moment, personal chapters he flags with a trigger warning, and then, through 2025 and 2026, "slowly working again."

The comeback video also covered hacking in 2026 and his answer to criticisms of AI. New uploads followed within weeks, including two on how OpenAI got hacked: once with an image, once with a one-year-old bug.

Fabian Faessler: Still a Wannabe

The joke in LiveOverflow's channel description was always that he was a wannabe hacker. A decade later the description still says so, the views are at 67 million, and plenty of the wannabes who learned from him are doing the job for real.

He built a company, then a school with Thomas Roth, then stepped away for the better part of three years. By the autumn of 2026 he was uploading again, with Hextree running alongside the channel.

The terminal is still scrolling.