Which among the following are the purposes of deploying a Firewall ? 1. Examine each packet arriving from Internet 2. Prevent unauthorised access 3. Block suspicious activity 4. Interconnect telephones Select the answer using the code given below :

The correct answer is D, 1, 2 and 3. A firewall inspects incoming traffic, keeps out unauthorised users and blocks suspicious activity, but it has nothing to do with connecting telephones. A firewall is a hardware device or software program that sits between a trusted network and an untrusted one such as the Internet. It examines each data packet against a set of security rules, checking its source, destination, port and, in advanced firewalls, its contents, and lets it through or drops it. In this way it prevents unauthorised access to computers and blocks suspicious connections, such as attempts to scan ports or reach known malicious addresses. Interconnecting telephones is the job of a telephone exchange or PBX, so statement 4 is incorrect. Option A is wrong because it leaves out blocking suspicious activity. Option B is wrong because it includes telephone interconnection and leaves out preventing unauthorised access. Option C is wrong because it leaves out packet inspection, the basic working of a firewall. Exam tip: firewall = filters network traffic by rules; antivirus = removes malware already on a device.