books, training or certifications.There are a lot of trainings available on the internet, Im saving some time for you:Some books and links to start (I put them in the order that I think is the best way to learn, feel free to choose the best way for you):https://en.wikipedia.org/wiki/Modern_Operating_Systemshttp://cse.hcmut.edu.vn/~minhnguyen/NET/Computer%20Networks%20-%20A%20Tanenbaum%20-%205th%20edition.pdfhttp://www.amazon.com/HTTP-Definitive-Guide-Guides/dp/1565925092https://www.edx.org/course/introduction-linux-linuxfoundationx-lfs101x-0 https://linuxacademy.com/linuxhttp://linux-training.be/http://www.htmlandcssbook.com/https://en.wikiversity.org/wiki/Programming_Logichttps://www.python.org/about/gettingstarted/https://www.perl.org/books/beginning-perl/http://www.sqlcourse.com/Now you have at least 6 months of studying ahead, and you can find by yourself more related trainings. Remember, google is your friend. I ALREADY HAVE THE SKILLS (Really? Double check it)So, if you already have the required skills, there are some good references that you can use to get into IT security, but first you should select one area and move to another one after you have mastered(my recommendation). However, sometimes you have to mix them in order to get better results. Some security areas (its not an exhaustive list): Web PentestingNetwork PentestingMobile PentestingSCADA PentestingReverse EngineeringMalware AnalysisForensics Security Research Hardware SecurityExploitation Of course, you can share your focus and studies more than 1 topic simultaneously. If you are thinking of using Kali to start your studies, you should visit the link http://docs.kali.org.In this link there is a lot of Kali documentation that can help you before you go to the #kali-linux channel on Freenode and ask an obvious question. Also, you can use forums.kali.org, additionally as Kali is Debian based it is a good idea to check the Debian Linux documentation if you are not familiar with this distro.Some useful links to start you pentest journey: Books:http://www.hackingexposed.com/ - Very nice book series that covers a lots different topics. This is another very nice book series that covers quite an amount of topics, like Mobile, Android, Cars and others, not only Web Applications, search for it.http://www.amazon.com/Web-Application-Hackers-Handbook-Exploiting/dp/1118026470http://www.amazon.com/s/ref=nb_sb_noss_1?url=search-alias%3Dstripbooks&field-keywords=hacker%27s+handbook&rh=n%3A283155%2Ck%3Ahacker%27s+handbookhttp://www.amazon.com/SQL-Injection-Attacks-Defense-Second/dp/1597499633/Also, you can google for Pentest Kali Linux in google, there are a lots of related books, just choose one and try. Links: One more link in the same style of this post:https://www.corelan.be/index.php/2015/10/13/how-to-become-a-pentester/http://www.vulnhub.com - > A lots of vulnerable machines to play.http://www.securitytube.com -> A lots of security videos and tutorials. https://www.cybrary.it -> More security videoshttps://pentesterlab.com -> Various pentest exerciseshttps://en.wikipedia.org/wiki/Hacking:_The_Art_of_Exploitation -> Low Level exploitationhttp://www.owasp.orghttps://github.com/enaqx/awesome-pentesthttp://worldwideprogramers.blogspot.com.br/2016/07/22-hacking-sites-ctfs-and-wargames-to.html?m=1Certifications: http://www.offsec.comhttp://www.elearn.comhttp://www.sans.orghttps://www.eccouncil.org/Certification/certified-ethical-hackerBuilding a pentest lab: https://pen-testing.sans.org/blog/2014/02/27/building-a-pen-test-infrastructure-hacking-at-home-on-the-cheaphttps://community.rapid7.com/docs/DOC-2196https://www.cybrary.it/0p3n/tutorial-for-setting-up-a-virtual-penetration-testing-lab-at-your-home/How To Ask Questions The Smart Way:http://www.catb.org/esr/faqs/smart-questions.htmlThanks to <Illusional> for the help! \o/