Starting Defensive Security , I suggest to read Offensive Security first .
Defensive Security is a part of cybersecurity in which providing security from unauthorized access or activity.
Explain with example : Our Country is a Company or Organization and our Army is Defensive Security which is provide Safety for our Country.
Defensive Security also known as a BLUE TEAMING .
Which task performing by Defensive Security ?
- Providing training Employees of the Company
- Checking all devices are proper.
- Updating System
- Fix the vulnerabilities if occure
- setting up protection devices like IPS , IDS , Firewall etc.
- Check system Logs and Maintaining Logs.
- and many more
SOC ( Security Operations Center ) , Threat Analyzer or Developer , Digital Forensics , Malware Developer or Analyzer are the Topics are part of Defensive Security.