Chapter 4 of 520% of exam

IT Security: Encryption, AAA, and Network Hardening

Security protects systems and data from unauthorized access, alteration, and disruption. IT support professionals must understand core principles, how encryption and authentication work, and the practical measures that reduce risk. This chapter builds the security mindset needed to defend everyday computing environments.

Security Principles and the CIA Triad

Security decisions are guided by a few enduring principles. The CIA triad and the principle of least privilege appear throughout security practice. Keeping these in mind helps evaluate any control or risk.

Confidentiality keeps data private

Only authorized parties should be able to access sensitive information, often enforced through encryption and access controls.

Integrity keeps data accurate

Data should not be altered by unauthorized parties, and mechanisms like hashing help detect tampering.

Availability keeps systems usable

Systems and data must be accessible when needed, which backups and redundancy help ensure.

Least privilege limits access

Granting users and processes only the access they need reduces the damage from compromised accounts or mistakes.

Encryption and Hashing

Cryptography protects data confidentiality and integrity. Encryption keeps information secret, while hashing verifies that data has not changed. Understanding the difference is fundamental to security work.

Encryption scrambles data

It converts readable plaintext into ciphertext using an algorithm and key, readable only by those with the correct key.

Symmetric uses one shared key

The same key encrypts and decrypts data, which is fast but requires securely sharing the key between parties.

Asymmetric uses key pairs

A public and private key pair allows secure communication without sharing a secret, underpinning HTTPS and digital signatures.

Hashing is one-way

A hash produces a fixed-length digest that cannot be reversed, used to verify integrity and store passwords securely.

Authentication, Authorization, and Accounting

Controlling access relies on the AAA framework. It verifies identity, decides what a user may do, and records their actions. Strong authentication such as MFA is a cornerstone of modern security.

Authentication verifies identity

It confirms a user is who they claim to be, using factors like passwords, tokens, or biometrics.

Authorization grants permissions

After authentication, authorization determines what resources and actions the user is allowed to access.

Accounting tracks activity

Logging user actions provides an audit trail useful for security monitoring and investigations.

MFA strengthens authentication

Requiring two or more independent factors means a stolen password alone is not enough to gain access.

Threats and Attacks

Defenders must understand common threats to guard against them. Many attacks target people rather than technology. Recognizing these threats is the first line of defense.

Malware harms systems

Malicious software including viruses, worms, trojans, ransomware, and spyware seeks to damage systems or steal data.

Phishing targets people

Fraudulent messages impersonate trusted sources to trick victims into revealing credentials or clicking malicious links.

Social engineering exploits trust

Attackers manipulate human psychology through impersonation, pretexting, and urgency rather than technical flaws.

Zero-days are unpatched flaws

A zero-day vulnerability is unknown to the vendor and has no patch when attackers begin exploiting it, making it especially dangerous.

Defensive Measures and Network Hardening

Practical controls reduce risk across systems and networks. Hardening removes unnecessary exposure, while good habits and tools protect users. Layering these defenses provides resilience.

Firewalls control traffic

They enforce rules on incoming and outgoing traffic, separating trusted internal networks from untrusted external ones.

Hardening reduces the attack surface

Disabling unused services, closing ports, and applying secure configurations makes systems harder to exploit.

Strong Wi-Fi encryption matters

Use WPA2 or WPA3 rather than the outdated, easily cracked WEP, together with a strong passphrase.

Good password hygiene protects accounts

Long, unique passphrases managed with a password manager, combined with MFA, defend against account compromise.

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Last updated: July 2026