Firewalls
Computer Science: OCR A Level, topic 3.3.18
Firewalls
It is important to monitor and filter data coming into and out of a network.
Firewalls
- A firewall is either a hardware device or a piece of software which sits between a device and the Internet.
- Firewalls inspect and filter incoming and outgoing data packets.
- They try to stop hackers gaining access to the network and stop malware getting into the network.
Packet filtering
- One role of the firewall is packet filtering.
- The firewall inspects each packet and drops those which do not meet certain criteria.
IP-address filtering
- The firewall only allows traffic from certain known sources.
- This can be used to prevent denial of service attacks.
Port-blocking
- Firewalls can block access to certain ports.
- One important port is port 22, which allows remote access via the Internet. By blocking this port, we can prevent hackers trying to take over the server.
Test yourself on Firewalls
Why is port 22 often blocked by the firewall?
Which of these are services offered by firewalls?