There are several great courses associated both with common e-learning destinations, such as Udemy, and prestigious security certifications, such as offensive security's Offensive Security Certified Professional (OSCP). They vary along several lines, including the required background, length, scope, and price. Taken together, they represent a kaleidoscope of security training options and philosophies.
Courses
Penetration Testing With Kali Linux
OSCP's penetration testing with Kali Linux class (https://www.offensive-security.com/information-security-training/penetration-testing-training-kali-linux/) is the required coursework for the OSCP certification, and comes with 30 days of access to the certification exam VPN...