Network Security Threats
Why Networks Are Vulnerable
When computers are connected into a network, and especially when connected to the internet, they become exposed to attack. The more connected a system, the larger its attack surface.
Main Categories of Threat
| Threat | Description |
|---|---|
| Malware | Malicious software that damages or gains unauthorised access to a system, see Malware |
| Brute force attacks | Systematically trying every possible password combination until the correct one is found |
| Data interception & theft | Intercepting data as it travels across a network (e.g., packet sniffing on unencrypted connections) |
| Social engineering | Manipulating people into revealing information or granting access, see Social Engineering |
Symptoms of an Attack
A device may be compromised if:
- Files are encrypted, corrupted or deleted
- The computer crashes, slows down or reboots spontaneously
- Internet connection becomes unusually slow
- Keyboard inputs are being logged and sent externally (keylogger)
Human Vulnerabilities (Careless Behaviours)
Many security breaches are caused by human error rather than technical exploits:
| Behaviour | Risk |
|---|---|
| Not installing OS updates | Leaves known security vulnerabilities unpatched |
| Not updating anti-malware | Cannot detect new threats |
| Not locking computer when away | Physical access by unauthorised users |
| Not logging off shared machines | Others can access your session |
| Using the same password across accounts | One breach compromises all accounts |
| Writing passwords on sticky notes | Physical theft of credentials |
| Sharing passwords | Others can impersonate you |
| Leaving printouts unattended | Physical data exposure |
| Misplacing storage media / laptops | Data loss or theft |
| Not securing wireless networks | Unauthorised network access |
| Not encrypting sensitive data | Data readable if intercepted |
| Not using security browser extensions | Exposed to malicious ads and scripts |
Brute Force Attacks
A brute force attack tries every possible combination of characters until the correct password is found.
- Automated tools can test millions of combinations per second
- Short or simple passwords are vulnerable
- Defence: Long, complex passwords; account lockout after failed attempts; multi-factor authentication
Password Reuse Risk
If you use the same password across multiple accounts:
- A data breach at one site exposes your password
- Attackers try the leaked password on other services (credential stuffing)
- Multiple accounts are compromised
Defence: Use a unique password for every account; use a password manager.
Exam Questions
Q: Describe a brute force attack.
A brute force attack tries every possible combination of characters for a password or passcode until the correct one is found. Automated tools can test millions of combinations per second.
Q: Explain the risk of reusing the same password across multiple accounts.
If one site suffers a data breach and the password is leaked, an attacker can try that password on other services. If the same password is used, multiple accounts could be compromised.
Exam Tip
Security questions often ask you to both describe the threat and explain a countermeasure. Always link them together, e.g., brute force → strong passwords + account lockout.