(Free) Virtual Networks (VPNs)
- ChaosVPN: http://wiki.hamburg.ccc.de/ChaosVPN
- Gh0st Networks: http://www.gh0st.net/
- Hacking Lab: https://www.hacking-lab.com/
- http://p0wnlabs.com/
- https://pwn0.com/
- PentestIT: https://lab.pentestit.ru/
Custom Personal Targets
- Hack A Server: https://hackaserver.com/
- Hack Me: http://hack.me/
- Hack This: https://www.hackthis.co.uk/
- Smash The Stack: http://smashthestack.org/
- Hack The Box: https://www.hackthebox.gr/
- SecAdvise: https://labs.secadvise.com/
- DarkHive: http://darkhive.net/
- Avatao: https://avatao.com/
- Root-Me: https://www.root-me.org/