Network Hardening Techniques
Network hardening techniques
What you will learn
- Recall core hardening steps: disabling unused ports and services, changing default credentials.
- Explain patch management's importance as ongoing hardening, not a one-time task.
- Explain ACLs' role in restricting traffic at the network level.
- Apply the attack surface reduction principle to a simplified scenario.
The attack surface is the sum of every point an attacker could try to enter from — every open port, running service, or account with default credentials adds to it. Hardening means shrinking that surface to the minimum actually needed to operate, not piling defenses on top of an unsolved problem.
A basic hardening checklist
1. Disable the unused
Turn off unnecessary ports and services on every device.
2. Change default credentials
The first thing any attacker tries is the factory-default username and password.
3. Keep patch management ongoing
A vulnerability fixed in an uninstalled update is still a real vulnerability.
4. Restrict traffic with ACLs
Allow only the traffic actually needed between network segments.
Core concepts
| Attack Surface | The sum of all potential entry points for an attacker — the smaller it is, the lower the risk. |
|---|---|
| ACL | A list of rules specifying which traffic is allowed through a router or switch and which is denied. |
What matters on the exam
- "Disable what's unused" is almost always the first step in hardening scenarios — before anything more complex.
- Patch management isn't a one-time task, it's an ongoing process for the system's whole lifetime.
Quick check
Answer in your head first, then reveal.
What's usually the first recommended hardening step for any new device?Reveal the answer
Changing the default credentials.
Why is patch management ongoing hardening, not a one-time task?Reveal the answer
Because new vulnerabilities are constantly discovered, and today's updates don't protect against tomorrow's.
What is an ACL's function?Reveal the answer
Specifying which traffic is allowed through a network device and which is denied.
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Sources
Used to verify the facts. The writing is original to Passuit.