Level Up Your OSINT Skills This December: The Ultimate 2025 Advent Calendar Challenge Guide

Hacker Noob Tips

01 Dec 2025 — 7 min read

December 2025 is here, and for cybersecurity enthusiasts, that means one thing: Advent Calendar CTF season! If you're looking to sharpen your OSINT (Open Source Intelligence) and cybersecurity skills while enjoying the festive season, you're in luck. This year brings an impressive lineup of free, educational challenges that run throughout the month.

Whether you're a complete beginner or a seasoned professional, these advent calendar challenges offer something for everyone. Let's dive into the best OSINT and cybersecurity advent calendars for December 2025.

Why Participate in OSINT Advent Calendars?

Before we jump into the specific challenges, let's talk about why these advent calendars are worth your time:

Daily Learning: New challenges each day keep you engaged and learning consistently
Free Education: All the platforms listed here offer completely free challenges
Community Building: Join thousands of other practitioners solving the same problems
Skill Development: Practice real-world techniques in a safe, legal environment
Career Advancement: Add new capabilities to your cybersecurity toolkit
Prizes & Recognition: Several platforms offer substantial prizes and certificates

The Top 2025 OSINT Advent Calendars

1. OSINT4Fun's Advent of OSINT 2025

Experience Level: Beginner to Intermediate
Duration: 24 days (December 1-24)
Website: https://www.osint4fun.eu/advent2025

OSINT4Fun returns for its third year with another stellar lineup. Created by OSINT enthusiasts and professionals from the Université d'Angers, this platform has established itself as a cornerstone of the OSINT learning community.

What Makes It Special:

24 carefully crafted challenges covering various OSINT techniques
Available in both English and French
Participate solo or form teams
Real-time rankings showing the top 20 fastest solvers
"First Blood" tracking for competitive players
Video walkthroughs by KrowZ posted daily on YouTube
Challenges remain accessible after December for continued learning

The platform emphasizes speed and accuracy, with rankings that showcase who drew first blood on each challenge. Even if you don't finish within the competitive window, all challenges stay available for learning at your own pace.

2. Bellingcat Open Source Challenge

Experience Level: Intermediate to Advanced
Duration: December (exact dates TBA)
Website: https://challenge.bellingcat.com/

Bellingcat, the renowned investigative journalism collective, launched their OSINT challenge platform in late 2024. After a successful first year engaging with the community, they're planning something special for December 2025.

What to Expect:

Monthly challenges typically release on the first Monday
High-quality, real-world oriented investigations
Professional-grade OSINT scenarios
Community discussion on their Discord server
Newsletter updates with tips and insights

While Bellingcat has been cryptic about their December plans (calling it a "special" set), their track record suggests it will be worth the wait. Keep an eye on their challenge page and join their Discord for announcements.

3. OSINT Switzerland's Santa Claus CTF

Experience Level: All levels
Duration: 24 days (December 1-24)
Website: https://ctf.osintswitzerland.ch

OSINT Switzerland, a dedicated community for open-source intelligence practitioners, is hosting their Santa Claus CTF for the second year running. This advent calendar challenges participants to help Santa solve mysteries and recover lost presents before Christmas.

Key Features:

24 daily challenges unlocking progressively
Engaging storyline that builds throughout December
Open to everyone globally, online participation
Team or individual participation
Community-driven learning environment
Active Discord server for collaboration

OSINT Switzerland has been building momentum in the community, having successfully hosted other events like the Haunted Pumpkin CTF earlier in 2025.

4. HEX ADVENT 2025

Experience Level: Intermediate to Advanced
Duration: 12 days (December 1-12)
Website: https://hex-advent.starlabs.sg

Here's an exciting newcomer! HEX ADVENT 2025 is a Christmas-themed CTF created by members of Singapore's female cybersecurity community and STAR Labs Singapore. This event brings diversity and fresh perspectives to the CTF landscape.

Challenge Categories:

Binary exploitation
Cryptography
Reverse engineering
Forensics
Web exploitation
OSINT challenges

Prize Structure (for eligible participants):

S$2,100 total prize pool for challenge completion
S$300 in best write-up awards (S$100 each for pwn, crypto, and RE challenges)
Free t-shirts for registered eligible participants
Eligibility: Women residing in Singapore or Malaysia

Important Notes:

Anyone can participate regardless of gender or location
Only women in Singapore/Malaysia are eligible for prizes
Mandatory write-ups required for top solvers (10+ challenges)
All challenges must be solved by December 31, 23:59 SGT for prize eligibility

This CTF is designed by women, for women, but everyone is encouraged to participate and learn. The write-up requirement is an excellent feature that promotes knowledge sharing and documentation skills.

5. TryHackMe's Advent of Cyber 2025

Experience Level: Beginner-friendly
Duration: 24 days (December 1-24)
Website: https://tryhackme.com/adventofcyber25

TryHackMe has been running Advent of Cyber since 2019, making it the longest-running cybersecurity advent calendar. With over 6 million learners worldwide, their platform is tried, tested, and beginner-friendly.

What's Included:

24 daily beginner-friendly challenges
Expert walkthrough videos for each challenge
Topics include: web exploitation, forensics, AWS security, malware analysis, password cracking, and more
Learn from renowned educators like John Hammond, DayCyberwox, Unix Guy, and Grant Collins
Certificate of completion
Over $150,000 in prizes through random drawings

Prize Information:

Each completed room = one entry into prize draw
Multiple room completions = multiple entries
Prize draw on January 7, 2026
Must be 16+ and have verified TryHackMe account
Winners contacted via email by January 30, 2026

Charitable Component: TryHackMe partnered with CyberSafe Foundation for 2025, donating laptops to underserved learners in Africa. Every challenge you complete contributes to this initiative, making your learning directly support cybersecurity education access globally.

While TryHackMe doesn't exclusively focus on OSINT, past events have included OSINT techniques in various challenges, making it valuable for well-rounded skill development.

How to Get the Most Out of These Challenges

1. Choose Your Approach

Completionist Path: Try to solve challenges from all platforms. This is ambitious but provides the broadest learning experience.

Focused Path: Pick 1-2 platforms that match your skill level and commitment level. Quality over quantity.

Casual Explorer: Pop in occasionally when a challenge topic interests you. These platforms usually keep challenges accessible after December.

2. Document Your Process

Create write-ups as you solve challenges. This helps you:

Solidify your learning
Build a portfolio of work
Contribute to the community
Potentially win prizes (especially relevant for HEX ADVENT)
Develop crucial documentation skills

3. Engage with the Community

Join Discord servers for each platform
Share insights (without spoiling solutions)
Ask questions when stuck
Help others after you've solved challenges
Build your professional network

4. Use Proper Tools

Make sure you have essential OSINT tools ready:

Reverse image search capabilities (Google Lens, TinEye, Yandex)
Social media investigation tools
Geolocation resources
Archive and cache viewers
Metadata extraction tools
OSINT framework bookmarks

5. Practice Ethical OSINT

Remember these critical principles:

Never harass or contact subjects of investigation
Don't access systems without authorization
Respect privacy and boundaries
Follow each platform's rules and guidelines
Keep findings within the challenge context

Time Management Tips

With potentially 60+ challenges available across all platforms, here's how to avoid burnout:

Set Realistic Goals: You don't need to complete everything. Choose 10-15 challenges as your baseline goal.

Schedule Time: Block 30-60 minutes daily rather than marathon sessions. Consistency beats intensity.

Prioritize by Interest: Start with topics that excite you. Engagement leads to better learning.

Use the Buddy System: Partner with a friend to keep each other accountable and share insights.

Remember It's Learning, Not Competition: The goal is skill development, not just scoreboard position.

What Skills Will You Develop?

Participating in these advent calendars will help you build:

Information Gathering: Finding needles in digital haystacks
Verification Techniques: Distinguishing fact from fiction
Geolocation Skills: Pinpointing locations from minimal clues
Social Media Intelligence: Ethically investigating online personas
Technical OSINT: Analyzing metadata, networks, and digital footprints
Analytical Thinking: Connecting disparate pieces of information
Tool Proficiency: Becoming efficient with OSINT platforms
Report Writing: Documenting findings professionally (especially if doing write-ups)

Beyond December: Continuing Your OSINT Journey

These advent calendars are fantastic, but they're just the beginning. Here are resources to continue learning:

Sofia Santos' OSINT Exercises: 30+ free challenges available year-round at gralhix.com
Bellingcat Monthly Challenges: Continue after December with their regular releases
Trace Labs CTFs: Quarterly events supporting missing person cases
CTFtime.org: Find ongoing CTF competitions globally
OSINT Framework: Comprehensive tool directory
Start.me Collections: Curated OSINT resource lists
YouTube Channels: Content from practitioners like Sofia Santos, Benjamin Strick, and others

Tools and Resources Checklist

Before diving in, make sure you have:

[ ] Web browser with privacy extensions
[ ] Virtual machine (recommended for isolation)
[ ] Note-taking system (Notion, Obsidian, OneNote)
[ ] Screenshots tool
[ ] Bookmarked OSINT tool collections
[ ] Social media accounts for investigation (burner/research accounts)
[ ] Discord app for community servers
[ ] Time blocked in your calendar
[ ] Snacks and coffee (optional but recommended)

Frequently Asked Questions

Q: I'm a complete beginner. Where should I start?
A: Start with OSINT4Fun or TryHackMe. Both are explicitly beginner-friendly with video walkthroughs to guide you.

Q: Can I participate in multiple advent calendars simultaneously?
A: Absolutely! Many people do. Just manage your time wisely and don't burn out.

Q: Do I need expensive tools or premium accounts?
A: No. All challenges can be solved with free, publicly available tools and resources.

Q: What if I can't solve a challenge?
A: Most platforms release solutions or walkthroughs. Use these as learning opportunities rather than failures.

Q: Can I win prizes from multiple platforms?
A: Generally yes, unless platform rules specify otherwise. Check individual terms and conditions.

Q: Will these challenges be available after December?
A: OSINT4Fun explicitly keeps challenges available. Others may remove or archive content, so try to participate during December when possible.

Final Thoughts

December 2025 offers an unprecedented opportunity to level up your OSINT and cybersecurity skills. With five major platforms running concurrent advent calendars, there's truly something for everyone regardless of skill level, time commitment, or learning style.

The OSINT community is built on collaboration, knowledge sharing, and continuous learning. These advent calendars embody those values while making education accessible to everyone globally, completely free of charge.

Whether you're looking to break into cybersecurity, enhance your current skill set, or simply enjoy puzzle-solving during the holidays, these advent calendars deliver. The community aspect adds immeasurable value through Discord servers, shared write-ups, and collective problem-solving.

Most importantly, remember that these challenges are about learning, not perfection. Every challenge you attempt, whether solved or not, builds your capabilities. Every tool you discover becomes part of your arsenal. Every technique you practice gets you closer to mastery.

So grab your coffee, fire up your browser, and get ready for an incredible month of OSINT learning. The challenges start December 1st, and the community is waiting for you!

Quick Reference Links

OSINT4Fun: https://www.osint4fun.eu/advent2025
Bellingcat: https://challenge.bellingcat.com/
OSINT Switzerland: https://ctf.osintswitzerland.ch
HEX ADVENT 2025: https://hex-advent.starlabs.sg
TryHackMe: https://tryhackme.com/adventofcyber25

Happy hunting, and may your December be filled with successful flag captures! 🎄🔍🎁

Have you participated in OSINT advent calendars before? What was your experience? Drop a comment below and share your favorite OSINT tools and techniques!

Looking for more OSINT resources year-round? Check out our other articles on cybersecurity investigation techniques, tool reviews, and industry trends.