http://www.janosgyerik.com/hacking-contest-on-a-live-cd/
https://www.pentestpractice.com/challenges
https://www.holidayhackchallenge.com/
https://github.com/Hackademic/hackademic/
https://www.amanhardikar.com/mindmaps/Practice.html
https://www.bright-shadows.net/
https://www.canyoucrackit.co.uk/
https://www.captf.com/practice-ctf/
https://www.chall.tasteless.eu/
https://www.codechef.com/contests/
https://www.counterhack.net/Counter_Hack/Challenges.html
https://www.cryptoclub.org/challenges/index.php
https://www.ctf.forgottensec.com/wiki/index.php
https://www.dftt.sourceforge.net/
https://www.exploit.co.il/projects/vuln
https://www.exploit-exercises.com
https://www.gendou.com/crypto/
https://www.hackergateway.com/
https://www.hacking-challenges.de/
https://www.hacksplaining.com/exercises
https://www.halls-of-valhalla.org/beta/challenges
https://www.hellboundhackers.org/
https://www.ismellpackets.com/category/packet-challenge/
https://www.javaist.com/rosecode/problems.php
https://microcorruption.com/login
https://www.netforce.nl/challenges/
https://www.newbiecontest.org/index.php
https://www.overthewire.org/wargames/
https://www.p0wnlabs.com/free/forensics
https://www.pentest.training/index.php
https://www.pentesterlab.com/exercises/
https://www.practicalpentestlabs.com/
https://www.praetorian.com/challenges/pwnable
https://www.pwnable.kr/index.php
https://www.questionengine.securitytreasurehunt.com/
https://www.root-me.org/lang=en
https://www.sabrefilms.co.uk/revolutionelite/
https://www.spoj.com/problems/classical/
http://www.trythis0ne.com/index.php
https://www.wargame.kr/challenge
/https://www.yashira.org/