Internet Security

Question 1

Name 5 methods of internet security.

Answer 1

• Firewalls
• Stateful inspection
• Encryption
• Proxy servers
• Packet filtering

Question 2

What are firewalls?

Answer 2

• They regulate the packets that pass through it, accepting or rejecting packets according to preconfigured rules
• Can work as a proxy server performing packet filtering and stateful inspection.

Question 3

What is stateful inspection?

Answer 3

• Stateful inspection examines a packets payload (instead of only the packets header) before deciding whether to allow it through the firewall.
• Use a connection table to keep track of rules set by the network administrator

Question 4

What are proxy servers?

Answer 4

• A proxy server sits between a public network and a private network.
• They hide the true network addresses of the sender from the recipient by using the IP address of the firewall rather than the sender’s private IP address
• This enables privacy and anonymous surfing
• Administrators can use proxy servers to filter the content users requests
• Proxy servers can also keep a log of users requests

Question 5

What is packet filtering?

Answer 5

• It accepts or blocks packets attempting to pass through the firewall based on their source IP address or the protocol they’re using (show by their port number)
• An administrator can specify specific IP addresses or protocols to block or use automatic filtering software that blocks suspicious packets.

Question 6

What is symmetric encryption?

Answer 6

In symmetric encryption, the sender and receiver share the same private key. The same key is used to encrypt and decrypt data sent between the two parties

Question 7

What is a major flaw in symmetric encryption?

Answer 7

-The sender and receiver must participate in a key exchange which can be vulnerable to interception.

Question 8

What is asymmetric encryption?

Answer 8

• Each device has a pair of mathematically related keys, the private key is kept secret and the public key is shared on the Internet.
• When a message is encrypted with a public key, only the corresponding private key can decrypt it

Question 9

How does asymmetric encryption avoid being vulnerable to interception.

Answer 9

-It uses a public and private, so there’s no key exchange, so the key can’t be intercepted

Question 10

What are digital signatures used for?

Answer 10

Used to verify

• the identity of the sender
• that the data has not been changed/corrupted during transmission.

Question 11

What type of encryption do digital signatures use?

Answer 11

Asymmetric encryption

Question 12

How are digital signatures created?

Answer 12

• Using a hashing/checksum algorithm a digest of the message being sent is created (the digest is dependant on the contents of the message)
• The digest is encrypted with the sender’s private key
• The encrypted digest is appended to the message
• The message + appended digest are encrypted
  with the recipient’s public key

Question 13

What happens when the recipient receives the message with the digital signature?

Answer 13

• They decrypt it using their private key; leaving them with the decrypted message + encrypted digest
• As the digest was encrypted using the sender’s private key, it can be decrypted using the sender’s public key.
• This verifies the sender’s identity as only they have access to their private key.
• The recipient then carries out the same hashing/ checksum algorithm on the message and checks
  if their result matches the decrypted digest.
• If everything matches, the recipient can be certain of the sender’s identity and that the data hasn’t be changed

Question 14

What is a digital certificate used for?

Answer 14

• It verifies ownership of a key pair used in asymmetric encryption
• Can be used to check that a fake key pair isn’t being used by an imposter

Question 15

Who issues digital certificates and what 5 things do digital certificates contain?

Answer 15

Issued by certificate authorities, digital certificates contain:

• a serial number
• the owner’s name
• an expiry date,
• the owner’s public key
• the certificate authority’s digital signature

Question 16

Name the three types of malware that can infect computers

Answer 16

• Trojan horses
• Worms
• Viruses

Question 17

What are worms?

Answer 17

• Worms are malware that can self-replicate between computers without the any user intervention.

Question 18

What are Trojan horses?

Answer 18

• A Trojan is malware that is disguised as a benign file that users are tricked into opening.
• Commonly spread as email attachments
• Commonly open a backdoor to your computer that the trojan creator can exploit

Question 19

What are Viruses?

Answer 19

• Viruses are self-replicating pieces of malware that rely on host files to spread copies of themselves between computers.

Question 20

How can we prevent malware?

Answer 20

• By installing anti-virus software (they scan and remove suspicious files on a computer)
• By updating software regularly
• Training people about the risks of opening suspicious email attachments or links
• Spam filtering

Question 21

What are two differences between viruses and worms?

Answer 21

• Viruses require a host, worms don’t

- Worms do not generally hide themselves inside another file