Collection of CTF challenges only the tricky ones are listed here.
- CTF Field Guide
- CTF Katana a list of tools with their use cases for CTF.
- GTFOBins is a curated list of Unix binaries that can be exploited by an attacker to bypass local security restrictions.]
- CTF101: An entry level for CTF with excellent explanation of the basics.
- CTF-Wiki: introduces range of common security flaws with examples.
- Network Forensics Training, Traffic analysis tutorials
- hacksplaining : Web application vulnerabilities illustrations.
- Splunk free fundamental course
- Burp suite online web security training
- MITRE ATT&CK training.