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Cas van Cooten

@casvancooten.com

604 followers 122 following 61 posts

@chvancooten on the bird app 🐦 --- Benevolently malicious offensive security enthusiast || OffSec Developer & Malware Linguist || NimPlant & NimPackt author || @ABNAMRO Red Team

Posts Replies Media

Cas van Cooten @casvancooten.com · 25/04/2025

Not thinking about infosec for a while 🥰

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Cas van Cooten @casvancooten.com · 18/04/2025

Pretty fun proof of concept - VS Code's `copilot-instructions.md` allows for blatant backdooring of agents if any AI agents or edits are run from an untrusted repository. It can seemingly fulfil the user's request, but actually implement (and hide) some nefarious side activities 😂

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Cas van Cooten @casvancooten.com · 31/03/2025

Touched down in Singapore! Looking forward to Black Hat Asia. Hope to see many of you around!

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Cas van Cooten @casvancooten.com · 18/03/2025

This must be the most informative graphic contained in the Microsoft docs learn.microsoft.com/en-us/opensp...

A diagram describing the negotiate protocol, only saying 'negotiate protocol' twice between client and server

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Cas van Cooten @casvancooten.com · 08/03/2025

I was invited to present Nimplant at Black Hat Asia 2025 in Singapore this April! If you're around, please do reach out to talk offensive development, modern programming languages, or how to use (or detect) Nimplant in your ops. Looking forward to it! www.blackhat.com/asia-25/arse...

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Cas van Cooten @casvancooten.com · 28/02/2025

Recently came across a pretty neat technique to silently load (malicious) VS Code extensions using its bootstrapping and portability features. Thought it was interesting enough to warrant my first blog post in 4 years 🙃 Check it out 👇 casvancooten.com/posts/2025/0...

casvancooten.com

Abusing VS Code's Bootstrapping Functionality To Quietly Load Malicious Extensions

Wow, been a while since my last blog 😅. During some research I came across a technique variation which I felt was interesting enough to share in a brief blog post. It relates to how the bootstrapping ...

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Cas van Cooten @casvancooten.com · 02/12/2024

Lol 75% thought leader, must be because I interact with @xpnsec.com too much 😂 blueskyroast.com/roast/casvan...

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Cas van Cooten @casvancooten.com · 26/11/2024

My ears were ringing when this was presented at RedTreat. Time for round two with this blog and tool release 😅 🔥

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Cas van Cooten @casvancooten.com · 19/11/2024

Looks like @rasta-mouse.bsky.social made it 👀 @xpnsec.com

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Cas van Cooten @casvancooten.com · 17/11/2024

Hello world! With Bluesky picking up steam I guess a (re-)introduction is in order. My name is Cas, I'm a red teamer at a big bank in the Netherlands. I like malware development (specifically in modern languages like Rust or Go) and learning more dev stuff every day. Content may include shitposts! 💜

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Cas van Cooten @casvancooten.com · 17/11/2024

Check out Jilles' starter packs for great infosec follows (NL + EN)!

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Cas van Cooten @casvancooten.com · 12/11/2024

This evening I'll be joining the HackTheBox Belgium meetup to speak about offensive development in modern languages. It should be fun, feel free to join! 🥳 www.meetup.com/meetup-group...

meetup.com

0x10 - Offensive Development In Modern Languages, Tue, Nov 12, 2024, 6:00 PM | Meetup

Instead of a machine walkthrough, we will welcome Cas Van Cooten to give his talk on "Offensive Development In Modern Languages"! It will be fully online and start at 6PM (

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