General CTF
- Net-Force | Challenges
 - https://ctfs.me/
 - http://www.wechall.net/challs
 - Mod-X Security Challenge
 - Welcome [Root Me : Hacking and Information Security learning platform]
 - https://picoctf.com/
 - http://hax.tor.hu/welcome/
 - Home - RingZer0 Online CTF
 - https://backdoor.sdslabs.co/
 - Shell-Storm repository
 - https://w3challs.com/
 - https://ctflearn.com/
 - https://ctf365.com/
 - https://www.hellboundhackers.org/
 - https://www.hackthis.co.uk/
 - https://www.enigmagroup.org/
 - Capture the Flag - Application Security Challenge
 - http://bright-shadows.net/
 - https://ctf101.org/
 - https://hackcenter.com
 - https://www.hackthissite.org/
 - https://www.rankk.org/
 - https://canhack.me/
 - Prügivedu
 - https://www.hackergateway.com/
 - https://www.wixxerd.com/challenges/
 - https://www.sabrefilms.co.uk/revolutionelite/
 - https://www.challengeland.co/#
 - https://ctf.hackerfire.com/
 - http://ctf.infosecinstitute.com/index.php
 
Web Exploitation
- https://hack.me/s/
 - http://www.gameofhacks.com/
 - https://join.eset.com/en/challenges
 - http://www.dvwa.co.uk/
 - http://google-gruyere.appspot.com/
 - http://www.hackertest.net/
 - http://solveme.peng.kr/
 - http://www.hacking-challenges.de/
 - https://redtiger.labs.overthewire.org/
 - https://www.hackthebox.eu/
 
Reverse Engineering
- https://microcorruption.com/
 - Reversing.Kr
 - MalwareTech Labs - Learn Reverse Engineering & Malware Analysis
 - https://crackmes.one/
 - https://challenges.re/
 - Crackmes | Reverse Engineering
 - https://join.eset.com/en/challenges
 - http://flare-on.com/
 - https://ropemporium.com/
 
Pwn
- http://pwnadventure.com/
 - https://exploit-exercises.com/
 - http://pwnable.kr/play.php
 - pwnable.tw
 - https://www.pentestpractice.com/
 
Wargames
- http://io.netgarage.org/
 - http://smashthestack.org/wargames.html
 - OverTheWire: Wargames
 - https://chall.stypr.com/
 - http://www.underthewire.tech/wargames.htm
 
Cryptography
- http://cryptopals.com/
 - https://id0-rsa.pub/
 - Electrica the Puzzle Challenge
 - try to decrypt - your brainteaser
 - https://www.cryptoclub.org/challenges/index.php