The Internet study guide

1. Trace a request across the Internet

Start with a URL and identify the domain name or FQDN within it. Explain that the domain name is a human-readable identifier, whereas an IP address is used to identify the destination for Internet communication. The DNS service is then involved in obtaining the relevant IP address from the Domain Name Server system. This distinction is important: DNS provides name information, while routers use addressing information to forward packets.

Next, describe packet switching. The data is divided into packets, each carrying the data and the necessary control information. Routers examine the addressing information and forward packets between networks. Because routing is performed across interconnected networks, packets can pass through multiple routers before reaching the destination. A gateway can be described as the connection point between networks, particularly where traffic enters or leaves a network. In an exam answer, link each device to its role rather than listing definitions separately.

2. Compare firewall mechanisms

When applying firewall knowledge to a situation, identify what information the firewall uses. Packet filtering applies rules to packet information. A proxy server is an intermediary, so the client communicates through it rather than directly with the other service. Stateful inspection uses the state of a connection as part of the decision. A strong answer explains why the selected mechanism is relevant to the traffic-control requirement, without treating all firewall methods as identical.

3. Reason about encryption and trust

For symmetric encryption, both parties require the same key for encryption and decryption, creating a key-exchange issue. For asymmetric encryption, the public key can be shared while the private key remains secret. Explain the key roles precisely and avoid reversing them. Digital certificates support confidence that a public key is associated with the claimed identity. Digital signatures use a private key and can be checked using the associated public key to provide evidence about the sender and whether the signed data has been changed. Keep certificates and signatures distinct: a certificate concerns identity and a public key; a signature concerns signed data and its claimed origin.

4. Apply malware protection

For a worm, trojan or virus question, identify the vulnerability being exploited and then connect a control to it. Improved code quality can reduce vulnerabilities in software. Monitoring can reveal suspicious behaviour or activity. Protection can help block, contain or remove malicious software. Avoid adding unsupported claims about a particular named attack or a specific law, product or statistic.

Self-check questions

1. Explain the difference between a URL, an FQDN, a domain name and an IP address.
2. Describe how DNS and routers contribute different stages to delivering a request.
3. Compare packet filtering, proxy-server operation and stateful inspection.
4. Explain the key-exchange problem for symmetric encryption and contrast it with asymmetric encryption.
5. Distinguish the purpose of a digital certificate from the purpose of a digital signature.
6. For each of a worm, trojan and virus, state that it is malicious software and explain how improved code quality, monitoring or protection could address exploited vulnerabilities.

For each answer, use a sequence of connected mechanisms: identify the component, state what it does, and explain how it contributes to the overall Internet or security process.