Network Security Concepts
Security concepts
What you will learn
- Explain the core CIA triad: confidentiality, integrity, and availability.
- Explain defense in depth through multiple layers.
- Recall the least privilege principle and its effect on limiting damage.
- Distinguish the traditional perimeter security model from zero trust.
Every security decision serves one or more of three goals: keeping unauthorized people from seeing data (confidentiality), ensuring it isn't modified without authorization (integrity), and ensuring authorized people can reach it when needed (availability). These goals sometimes conflict — very strong encryption can slow legitimate access — and good security balances rather than maximizes just one.
The CIA triad
| Confidentiality | Preventing unauthorized access to data — usually via encryption and access control. |
|---|---|
| Integrity | Ensuring data hasn't been altered or corrupted without authorization, and detecting any such attempt. |
| Availability | Ensuring authorized users can reach data and service when needed — directly supported by HA and DR. |
Defense in depth layers
1. Perimeter
The firewall at the network's external boundary.
2. Network
VLAN segmentation and access control lists within the network itself.
3. Host
Antivirus and local firewall on each device.
4. Application and data
Application-level access control, and encryption at rest and in transit.
The zero trust myth
Zero trust isn't just "a stronger VPN" — it's a shift in the base assumption: no device or user is automatically trusted just for being inside the network; every access attempt is verified every time, regardless of its location.
Quick check
Answer in your head first, then reveal.
Which CIA goal does encryption primarily serve?Reveal the answer
Confidentiality.
What is the least privilege principle?Reveal the answer
Granting each user or system only the minimum permissions needed to do its job.
What basic assumption does the zero trust model reject?Reveal the answer
That any device or user inside the network is automatically trustworthy.
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Sources
Used to verify the facts. The writing is original to Passuit.