Security CTFs (capture the flag) are competitions where people race against eachother to find "flags" by hacking web apps, reverse engineering, breaking weak crypto, doing crazy OSINT.

They're fun, and they everyone you learn a lot from different fields (fx. CAN, recovering keystrokes from a keyboard's captured traffic, CSS exfiltration, etc). You'll also meet a lot of smart people and maybe make some friends.

If you'd like to have some fun this weekend, one of the most well put together (in terms of challenges) CTFs is running: https://xmas.htsp.ro/home

CTFtime is the main hub for CTFs: https://ctftime.org/calendar/

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Edit (0) - Last year's challenges and write-ups: https://ctftime.org/event/926/tasks/