It’s that time of the year again! An entire month dedicated to learning, exploring, and putting your OSINT skills to the test with daily challenges and Capture the Flag (CTF) events. Are you ready for a busy end of 2025?
Similarly to last year, we are once again spoiled for choice with multiple platforms preparing exciting OSINT Advent calendars across a variety of topics. Starting December 1st, 2025, dozens of cybersecurity and OSINT challenges will be released, daily, all for free, with some offering prizes to those who have proven themselves worthy (and eligible)!
Without further ado, here is my top 2025 OSINT Advent calendar list:
🎄🗓️🔎
Who?
OSINT4Fun’s Advent of OSINT 2025.
This project is not new to the game having already (successfully) created two previous editions of OSINT Advent calendars. This year they’re back for more!
What?
Various OSINT enthusiasts and professionals once again created 24 challenges for the OSINT4FUN Advent of OSINT 2025. All challenges will be available in French and English. People can participate individually or in teams, and you do not need to register to access them, only if you want to see how you ranked against others. The ranking showcases the top 20 fastest users and how many times they dew “first blood” so speed counts as much as accuracy! I have, once again, prepared two OSINT challenges for this fun Advent calendar, and I sincerely hope you enjoy them.
Where?
OSINT4Fun’s Advent of OSINT 2025 can be found on:
https://www.osint4fun.eu/advent2025
When?
Starting from the 1st to the 24th December 2025. The challenges will remain available and accessible afterwards.
🎄🗓️🔎
Who?
Bellincat Open Source Challenge.
At the end of 2024, Bellingcat made their OSINT challenges’ debut with a set of five tasks hosted on their new subdomain. After twelve months of successfully engaging with the community I heard they’re ready for more.
What?
Something is cooking at Bellingcat’s challenge page. I have heard from a good source that the December OSINT challenges won’t be “business as usual.” My suggestion is to keep your eyes peeled and perhaps check out their Discord server or newsletter for tips and updates. I do love a good mystery.
Where?
The Bellingcat challenge page seems to be a good place to start:
https://challenge.bellingcat.com/
When?
That is for me to know and you to find out. I’m joking, I also don’t know.
Bellingcat releases their monthly OSINT challenges on the first Monday of the month so I suppose that the “special” December 2025 set won’t be any different.
🎄🗓️🔎
Who?
HEX ADVENT 2025. We have a new player in the game and I’m for it!
This year, members of the Singapore’s female cybersecurity community, and female co-workers from STAR Labs, a Singapore cybersecurity company, created their first cybersecurity Advent CTF.
What?
This Christmas themed CTF is designed by women and for women but even if you don’t fit the criteria don’t let that stop you from participating!
The HEX ADVENT 2025 has more than just OSINT challenges with users having to showcase their skills in binary exploitation, cryptography, reverse engineering, forensics, and web exploitation as well.
Anyone, regardless of gender or location, can participate in this event, however, if you are a woman residing in Singapore and Malaysia, you are eligible to win prizes! With the project also awarding S$100 each for the three best write-ups, I’m eager to add “reading CTF walkthoughs” to my December to-do list.
Where?
The HEX ADVENT 2025 Christmas themed CTF can found here:
https://hex-advent.starlabs.sg/
When?
The challenges for this Christmas CTF will be unveiled daily over the course of 12 days, starting from the 1st of December 2025.
🎄🗓️🔎
Who?
TryHackMe’s Advent of Cyber 2025.
This platform is a well know player in the field having hosted multiple Advent Of Cyber events since 2019. They are aimed at beginners and are a good place to kickstart your cybersecurity adventure.
What?
The TryHackMe platform is once again hosting their Advent Of Cyber. There will be multiple ways to test your cybersecurity skills with these beginner friendly challenges. And if you’re stuck, you can always watch the walkthrough videos recorded by experts. The website doesn’t specifically mention that there will be OSINT challenges to be solved in 2025; but don’t let that stop you as you’ll likely have to, similarly to previous years, use your OSINT skills to solve some of the tasks.
With prizes worth over $150,000 and the ability to get a shinny new certificate to brag about, why not give it a go?
Where?
TryHackMe’s Advent of Cyber 2025 can be found here:
https://tryhackme.com/adventofcyber25
When?
TryHackMe’s Advent of Cyber 2025 will officially start on the 1st of December 2025, with new challenges everyday up until Christmas.
🎄🗓️🔎
Some people love Christmas because it’s a joyous time of the year to spend with their loved ones, exchange gifts, and indulge in delicious food. But not me, I’m here for the OSINT Advent calendar challenges! It’s the best time of the year to upgrade your skills and be a part of this amazing community. I truly appreciate the time and effort so many people have put into developing these creative CTFs and challenges. I may not be able to solve them all, but I know that I’ll be starting 2026 with a new set of skills.
I wish you all a great December 2025.
~Sofia.
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