FIREWALL

Question

Answer 1

A firewall is a network security system that monitors and controls the incoming and outgoing network traffic based on predetermined security rules

Firewalls filter the traffic that flows into you PC or your network through a internet connection. They sift through the data flow & block that which they deem (based on how & for what you have tuned the firewall) harmful to your network or computer system.

When connected to the internet, even a standalone PC or a network of interconnected computers make easy targets for malicious software & unscrupulous hackers. A firewall can offer the security that makes you less vulnerable and also protect your data from being compromised or your computers being taken hostage.

Now coming to question

Option b and c are correct.

Firewall block incoming traffic so d is likely correct .

HTTP is an application layer protocol. Since firewal is at layer 4, it cannot block HTTP data.

So option a is correct here.

Comments

ManojK layer 4 firewall can look at source port no, destination port no and thus block an HTTP service(looking at port no 80 in destination port no field of tcp header, thus discarding pkts).

since layer 4 firewall doesn't deals with Application layer , it can't differentiate between users in multi-user system(based on username and passwords), thus can't block TCP traffic from a specific user on a multi-user system.

D should be the ans.

Answer 2

The firewall can filter traffic upto Transport Layer (Given in the question.)

Only HTTP among the given options is an Application Layer Protocol. Which is above Transport Layer.

ICMP, IP are network layer protocols. TCP is a transport Layer protocol.

Hence, Option A is correct.