No.499
I used to do challenges from crackmes.de but it seems to be dead. You can try this mirror:
http://crackmes.cf/ No.533
You might be remembering
http://root-me.org/ which has some good reversing challenges.
No.1156
>>499https://crackmes.one/ seems to be somewhat better. It's still dead but at least it has an usable search interface. Now only if you could filter by architecture…