(Information rovided by @Mod Derek from Security Blue Team Discord from Daniel Durnea on the Offensive Security Facebook page - I am not the original author of this information)
Below are 5 skills which you have to improve before registering for OSCP
- Learn basic of Computer Network, Web application, and Linux
- Learn Bash and Python scripting
- Enumeration is key in OSCP lab, I repeat Enumeration is key in OSCP Lab and in real world too
- Download vulnerable VM machines from vulnhub
- Buffer Overflow (BOF) exploitation
Below are the free reference before registration of OSCP
https://www.cybrary.it/course/ethical-hacking/
https://www.cybrary.it/course/web-application-pen-testing/
https://www.cybrary.it/course/advanced-penetration-testing/
https://www.offensive-security.com/metasploit-unleashed/
https://www.cybrary.it/course/python/
Below are the reference for Buffer overflow and exploit developmet for OSCP http://www.fuzzysecurity.com/tutorials/expDev/1.html
https://www.corelan.be/index.php/2009/07/19/exploit-writing-tutorial-part-1-stack-based-overflows/
**For Bash Scripting ** http://www.tldp.org/LDP/Bash-Beginners-Guide/html/
Transferring Files from Linux to Windows & post-exploitation
https://blog.ropnop.com/transferring-files-from-kali-to-windows/
https://www.cybrary.it/course/post-exploitation-hacking/
Privilege Escalation:
http://www.greyhathacker.net/?p=738
http://www.fuzzysecurity.com/tutorials/16.html
https://github.com/GDSSecurity/Windows-Exploit-Suggester
http://pwnwiki.io/#!privesc/windows/index.md
https://blog.g0tmi1k.com/2011/08/basic-linux-privilege-escalation/
https://github.com/rebootuser/LinEnum
https://www.youtube.com/watch?v=PC_iMqiuIRQ
Port redirection/tunneling
https://chamibuddhika.wordpress.com/2012/03/21/ssh-tunnelling-explained/
http://www.abatchy.com/search/label/Networking
Practice Lab online & offline Most of this lab help you to understand different attack and (privilege escaltion very very important for OSCP )
http://overthewire.org/wargames/bandit/
https://www.vulnhub.com/?q=kioptrix&sort=date-asc&type=vm
https://www.vulnhub.com/entry/fristileaks-13,133/
https://www.vulnhub.com/entry/brainpan-1,51/ (Buffer overflow vm)
https://www.vulnhub.com/entry/mr-robot-1,151/
https://www.vulnhub.com/entry/hacklab-vulnix,48/
https://www.vulnhub.com/entry/vulnos-2,147/
https://www.vulnhub.com/entry/sickos-12,144/
https://www.vulnhub.com/entry/devrandom-scream,47/