4.2.1 - Network vulnerabilities and protection

Why network security matters

A school network may hold attendance records, assessment results and staff files while also providing services used throughout the day. A security failure could expose private data, change information so it is no longer trustworthy, or make a service unavailable when people need it.

A vulnerability is a weakness in a system or its security controls that could be exploited. A shared administrator password, an unlocked server room and an over-permissive firewall rule are all weaknesses. The attacker or event that might exploit a weakness is a threat; it is not the vulnerability itself.

Network security matters because it helps preserve three useful properties:

• Confidentiality: data is seen only by people who are authorised to see it.
• Integrity: data remains accurate and is changed only in authorised ways.
• Availability: authorised users can reach data and services when needed.

Suppose an attacker changes students' assessment results. Saying only that "the network has been hacked" does not explain the impact. A developed Paper 1 answer is: the integrity of the results is lost, so teachers could make decisions using inaccurate data. The first idea identifies what is harmed; the second gives the linked consequence.

Authorised security testing

Organisations should look for vulnerabilities before a malicious attacker finds them. They can give a trusted tester permission to use attacker-style techniques in a controlled way.

The word ethical depends on more than good intentions. The tester needs explicit permission, must stay inside an agreed scope and must handle any findings responsibly. Testing a system without permission, or continuing beyond the agreed limits, is not ethical hacking.

The two terms overlap. Ethical hacking describes the authorised, defensive purpose and behaviour; a penetration test is a structured testing activity that an ethical hacker may carry out.

A sensible testing cycle is:

1. agree written permission, the systems that are in scope, the time of the test and actions that are not allowed;
2. attempt to bypass the selected security controls using agreed attacker-style techniques;
3. record evidence of each weakness without causing unnecessary harm or accessing unrelated data;
4. report the vulnerability and its possible effect so the organisation can correct it;
5. retest the correction if required.

For example, a school authorises a tester to check whether a normal pupil account can reach a test copy of a staff folder. The tester stays within that scope, demonstrates that the folder permissions are too broad and reports the evidence. The school changes the permissions and checks them again. The penetration test identified the vulnerability; the later configuration change protected the network.

Access control

Once a person tries to use a network, the system must decide both who the person is and what that person is allowed to do.

There are two related decisions:

• Authentication checks that a user is who they claim to be, for example with unique sign-in credentials and, where appropriate, an additional factor.
• Authorisation decides which resources and actions that authenticated user is permitted to access.

These decisions are not interchangeable. A pupil may authenticate successfully with the correct account but still be unauthorised to open the payroll folder.

Good access control gives each account only the permissions needed for its role. This is sometimes called the principle of least privilege. Accounts and permissions should also be removed when they are no longer needed.

Suppose a pupil account can open payroll files and install software across the network. The correction is not merely to change the pupil's password: the account's permissions must be reduced. If those credentials are later misused, the intruder is then limited to the resources available to a pupil rather than receiving unnecessary high-level access.