Network Security Quiz

 Q1: The Multimedia Internet Mail Extension (MIME) is used to allow non-ASCII content such as an image to be sent using email. Which of the following is NOT performed in order to allow for non-ASCII content to be sent?

A. Encrypt the non-ASCII content
B. Encode the non-ASCII content to ASCII format
C. Specify the encoding method in the email header
D. Specify the type of non-ASCII content in the email header

Solution: TLS

Q2: When DomainKeys Identified Email (DKIM) is used, what is stored in the DNS server that needs to be retrieved by the receiving email server?
A. Email policy specified by the sending domain
B. List of email servers that are authorized to send email from the sending domain
C. Public key of the email sender domain
D. Public key of the DNS server

Solution: Public key of the email sender domain

Q3: Which of the following data transfer is NOT done using the SMTP protocol?
A. Send email from an email client application to sender's email server
B. Transfer email message from the receiver's mailbox to the receiver's user agent
C. Send email from the sender's email server to the receiver's email server
D. Forward email from one email server to another email server

Solution: Transfer email message from the receiver's mailbox to the receiver's user agent

Q4: Which of the following S/MIME service - mechanism pair is NOT correct?
A. Integrity - hashing
B. Integrity - digital signature
C. Confidentiality - symmetric cryptography
D. Authentication - public key infrastructure (PKI)

Solution: Integrity - digital signature

Q5: To send email to the address salman@uniten.edu.my, the sender's email server needs to find the IP address of the receiver's email server (i.e. uniten.edu.my). Which DNS resource record type contains this information?
A. MX
B. A
C. NS
D. MAIL

Solution: MX

Q6: Which security objective is compromised when a transmitted email is read by an attacker during its transmission?
A. Authenticity
B. Accountability
C. Integrity
D. Confidentiality

Solution: Confidentiality

Q7: When SPF (Sender Policy Framework) is used, what is stored in the DNS server?
A. Public key of the email receiver domain
B. Public key of the email sender domain
C. Email server(s) authorized to send email for particular domain
D. Policy specified by the email sender

Solution: Email server(s) authorized to send email for particular domain

Q8: Which of the following use of encryption keys in S/MIME is not correct?
A. Receiver's public key: encrypt the secret key
B. Sender's private key: encrypt the hash value
C. Secret key: encrypt the email content
D. Symmetric key: encrypt the email header

Solution: Symmetric key: encrypt the email header 

Q9: The command STARTTLS is executed when this TLS mode is used:
A. Start TLS mode
B. Explicit TLS mode
C. Implicit TLS mode
D. Normal TLS mode

Solution: Explicit TLS mode

Q10: In which of the following situations it is more suitable to use AH instead of ESP?
A. When the main security concern is passive attack
B. When the packet carries authentication information such as login credential
C. When communication is done between two hosts instead of a host and a firewall/router
D. When the IP payload is TLS data

Solution: When the IP payload is TLS data

Q11: If IPSec is to be used to configure a VPN between a remote worker using a laptop and the main office, which of the following IPSec protocols and modes that should be used?
A. AH tunnel mode
B. ESP tunnel mode
C. ESP transport mode
D. AH transport mode

Solution: ESP tunnel mode

Q12: When two hosts are communicating using IPSec, the information regarding whether they are using AH or ESP is specified in:
A. IP header of the transmitted packets
B. The digital certificate used by the sender and receiver
C. IPSec policy configured on both the sender and receiver
D. Security association used by the communication

Solution: Security association used by the communication

Q13: The use of private IP provides security in which of the following ways?
A. It prevents hosts using private IP addresses from being directly accessed by attackers in the Internet
B. It prevents hosts with private IP addresses from accessing insecure websites in the Internet
C. It prevents other intranet hosts from directly accessing hosts using private IP addresses
D. It prevents malware from being downloaded into hosts using private IP addresses

Solution: It prevents hosts using private IP addresses from being directly accessed by attackers in the Internet

Q14: What is the main motivation behind the development of IPv6?
A. The realization that the IPv4 address space is going to be used up
B. To provide a more secure IP protocol
C. To improve the speed of the Internet traffic
D. To catch with the use of modern networking technology and equipment

Solution: The realization that the IPv4 address space is going to be used up

Q15: You are configuring a communication between two servers. You would like to use IPSec to ensure that the two servers are not replaced by a different server, and they should stop communicating if that happens. Which of the following IPSec protocols and modes that should be used?
A. AH in transport mode
B. AH in tunnel mode
C. ESP in tunnel mode
D. ESP in transport mode

Solution: AH in transport mode

Network Security Quiz

 Q1: The use of HTTPS ensures the following EXCEPT

A. Confirms that the browser is a communicating with an authentic web server
B. Hides the IP address of the user's computer
C. The website content downloaded is encrypted and cannot be read
D. HTTP header is encrypted and cannot be read

Solution: Hides the IP address of the user's computer

Q2: What is the purpose of MIME extension in email application?
A. To authenticate the email sender
B. To encrypt the email content
C. To enable email to send attachments
D. To enable email to carry ASCII contents

Solution: To enable email to send attachments

Q3: The following are true about private IP addresses EXCEPT:
A. The address block 172.16.0.0/12 belongs to one of the private IP address blocks
B. Accessing the Internet requires the use of Network Address Translation (NAT)
C. A private IP address used in an organization may also be used in another organization
D. They can be directly accessed from the Internet

Solution: They can be directly accessed from the Internet

Q4: Given below are examples of network attack surface EXCEPT:
A. A corporate firewall that is configured to allow incoming connection on port 80
B. A corporate firewall that is configured to allow outgoing connection on port 80
C. A telnet service running on a public Web server
D. A login page on a website that does not use TLS

Solution: A corporate firewall that is configured to allow outgoing connection on port 80

Q5: Which of the following is a type of passive security attack?
A. Masquerade
B. Traffic analysis
C. Denial of service
D. Replay

Solution: Traffic analysis

Q6: The feature of SSH that enables any insecure TCP connection to be converted to a secure SSH connection is called ____________.
A. Port forwarding
B. Remote login
C. Channel conversion
D. Securing channel

Solution: Port forwarding

Q7: Which of the following email security threats can be prevented using DNSSEC?
A. Email sent is transmitted to the attackerʼs server
B. Email cannot be sent due to DoS attack
C. Email sent is sniffed during transmission
D. Email sending address is spoofed

Solution: Email sent is transmitted to the attackerʼs server

Q8: Which of the following is NOT a TLS record protocol payload?
A. Application data
B. Alert protocol
C. Hello protocol
D. Change cipher spec protocol

Solution: Hello protocol

Q9: Given below are security services offered by the Authentication Header (AH) protocol in IPSec EXCEPT:

A. Confidentiality
B. Integrity
C. Access control
D. Authentication

Solution: Confidentiality

Q10: DNSSEC ensures the following security objective(s):
A. Authenticity and confidentiality
B. Confidentiality, integrity and authenticity
C. Integrity and authenticity
D. Confidentiality and integrity

Solution: Integrity and authenticity

Q11: Given below are part of the Internetʼs network layer EXCEPT:
A. The TCP protocol
B. The IP protocol
C. The routing protocols
D. The ICMP protocol

Solution: The TCP protocol

Q12: Given below are ways by which we can secure email application EXCEPT:
A. Configure email client to run SMTP and IMAP over TLS
B. Configure email client to use S/MIME
C. Configure email client to use IPSec
D. Configure email server to use SPF, DKIM and DMARC

Solution: Configure email client to use IPSec

Q13: Which of the following protocols is used to set up a security association (SA)?
A. Security Association Connection (SAC)
B. Authentication Header (AH)
C. Encapsulating Security Payload (ESP)
D. Internet Key Exchange (IKE)

Solution: Internet Key Exchange (IKE)

Q14: Given below are among the security concerns to an Internet user EXCEPT:

A. An attacker may sniff your packets
B. You may not be communicating with the person that you think you are communicating with
C. Your Internet connection may not be fast enough that an attacker may capture your slow moving packet
D. Malware may be secretly installed on your computer

Solution: Your Internet connection may not be fast enough that an attacker may capture your slow moving packet

Q15: The security protocol used in HTTPS is _____________.
A. TLS
B. DNSSEC
C. IPSec
D. SSH

Solution: TLS

Q16: The use of HTTP proxy can prevent _____________.
A. the web server from knowing the IP address of the computer running the Web browser
B. an attacker from modifying an HTTP reply message
C. an attacker from sniffing the HTTP messages sent between the web browser and server
D. hijacking of an HTTP session

Solution: the web server from knowing the IP address of the computer running the Web browser

Q17: A security policy database (SPD) may contain the following information EXCEPT:
A. Security parameter index (SPI)
B. Remote IP address and port number
C. Local IP address and port number
D. Action to be taken

Solution: Security parameter index (SPI)

Q18: Which of the following fields is not encrypted in Encapsulating Security Payload (ESP) transport mode?
A. ESP trailer
B. TCP header
C. IP header
D. TCP data

Solution: IP header

Q19: The SSH protocol was initially developed for the purpose of:
A. File transfer
B. Remote program execution
C. Sending email
D. Remote login

Solution: Remote login

Q20: Which of the following is one of the differences between S/MIME and OpenPGP?
A. S/MIME uses certificates issued by Certificate Authority while OpenPGP generates their own public and private keys
B. S/MIME provides authenticity and confidentiality, while OpenPGP only provides confidentiality
C. S/MIME does not include the senderʼs public key with the message, while OpenPGP includes the senderʼs public key with the message
D. OpenPGP provides authenticity and confidentiality, while S/MIME only provides authenticity

Solution: S/MIME uses certificates issued by Certificate Authority while OpenPGP generates their own public and private keys

Q21: Given below are part of the Internet’s network layer EXCEPT

A. The IP protocol
B. The routing protocols
C. The TCP protocol
D. The ICMP protocol

Solution: The TCP protocol

Q22: Which of the following is NOT one of the reasons why TLS has become the most popular network security protocol?
A. TLS is independent of operating system platform
B. TLS is used to secure the Web application, which is the most used network application
C. TLS only needs to be configured once, and all network applications running on the host would then be protected
D. From a user point of view, using TLS is as easy as downloading and using a client application that implements TLS

Solution: TLS only needs to be configured once, and all network applications running on the host would then be protected

Q23: Which of the following email security mechanisms can be configured by an email user?
Select one:
A. DKIM
B. SPF
C. DANE
D. PGP

Solution: PGP

Q24: Which of the following is an advantage of using IPsec (which is network-layer security protocol) as compared to using TLS (which is a transport-layer security protocol)?
A. Configuration of IPsec is easier compared to TLS
B. IPsec uses more secure cryptographic protocols compared to TLS
C. Once IPsec is configured, communication will all Internet hosts will be protected
D. Once IPsec is configured, data transfer of all network applications with the specified receiving host will be protected

Solution:  Once IPsec is configured, data transfer of all network applications with the specified receiving host will be protected 

Q25: Which of the following is NOT true about the use of explicit TLS in email application?
A. Before secure connection is achieved, port 25 is used by SMTP client to connect to SMTP server
B. When explicit TLS is used, email message sent between an email client and an email server is encrypted
C. It requires an insecure SMTP connection to be upgraded to a secure connection using the STARTTLS command
D. Explicit TLS can be used not only by SMTP, but also by IMAP and POP3

Solution: Before secure connection is achieved, port 25 is used by SMTP client to connect to SMTP server

Q26: The use of https prevents the following attacks from being conducted EXCEPT:
A. Attacker replacing the Web server with a malicious server
B. Attacker sniffing the username and password transmitted by Web browser
C. Attacker stealing the HTTP cookie transmitted in an HTTP request message
D. Attacker spoofing the IP address of the host on which the Web browser is running

Solution: Attacker spoofing the IP address of the host on which the Web browser is running

Q27: What is contained in an HTTP cookie?
A. A string that specifies the type of Web browser used by the user
B. The username and password of the Web user in cleartext
C. A string that identifies the Web user
D. The username and password of the Web user in encrypted form

Solution: A string that identifies the Web user

Q28: Which of the following is NOT true about DNS-based Authentication of Named Entities (DANE)?
A. It solves security issues related to the use of STARTTLS
B. It encrypts the email data regardless of whether the email server supports TLS or not
C. It ensures the authenticity of an email server without verifying the server's digital certificate with a Certificate Authority (CA)
D. It makes use of a DNS record called TLSA

Solution: It encrypts the email data regardless of whether the email server supports TLS or not

Q29: In S/MIME, what is the use of the receiver's private key?
A. To encrypt the message digest
B. To decrypt the message content
C. To decrypt the message digest
D. To decrypt the secret key
E. To encrypt the message content
F. To encrypt the secret key

Solution: To decrypt the secret key

Q30: In S/MIME, what is the use of the receiver's public key?
A. To decrypt the secret key
B. To decrypt the message content
C. To encrypt the message digest
D. To encrypt the message content
E. To decrypt the message digest
F. To encrypt the secret key

Solution: To encrypt the secret key

Q31: Differentiate between active and passive security attacks.

Solution: 

Passive security attack: In this attack the intruder or attacker just sniffs the information, he does not modify or change it. He only listens to the traffic and compromises the confidentiality of the data

Active Security attack: In this the attacker first listens to the information and then changes it and then forwards it to the receiving party which means the confidentiality and integrity both compromises. 

Q32: If you perform a port scan, and see that a port is opened on the host, what does that tell you?

Solution: Open port tells that the port or the network is actively accepting packets and indicates that it is listening

Q33: Both Sender Policy Framework (SPF) and DomainKeys Identified Email (DKIM) are used to prevent the email sending address from being spoofed. However, the techniques used are different. Differentiate between the techniques used by these two mechanisms.

Solution: SPF makes use of a TXT DNS resource log in which the sending domain identifies all of the domain's senders. To authenticate the sender, the receiver will query a TXT DNS resource record about the sender's address domain and IP address. DKIM, on the other hand, uses a digital signature. The sender's private key will be used to sign the message. The receiver would then search the public key to see if the message is from the legitimate sender 

Q34: HTTP cookie is a useful mechanism for Web application and can provide various functionalities to the Web application. However, it has a number of security issues.
(a) If you are logged in to a web application, HTTP cookie is used to maintain your login session. What could happen if an attacker manage to capture the cookie?
(b) What is the solution to the problem mentioned in (a) above?
(c) Explain ONE (1) more security issue related to the use of HTTP cookie.

Solution: a) Attacker could steal user session ID and perform session hijacking where attacker can later perform any action that the active user is authorized to do.
b) To solve the problem of unencrypted format for cookies the owner of the web application should use HTTPS with a digital certificate but for me, I should delete the cookies and log out after I finish using the session.
c) If an attacker steals the http cookie, the attacker can view user's browsing history and monitor user's activities. This compromises confidentiality.

Q35: For each of the following situation, identify the most suitable IPSec protocol (AH or ESP) and mode (transport or tunneling) to be used.
(a) A staff working from home during COVID-19 pandemic, and would like to establish a Virtual Private Network (VPN) to his corporate network.
(b) A system administrator configuring two servers that always send data to each other. The system administrator needs to ensure that the data transmitted between the two servers cannot be read by an attacker.
(c) A system administrator configuring firewall between two office branches. The data transmitted are all TLS data. The main aim of using IPSec would be to ensure the authenticity of the two firewalls. 

Solution: a) ESP tunnel mode
b) ESP transport mode
c) AH tunnel mode

The following character encoding is used in a data link protocol

Q: The following character encoding is used in a data link protocol:

A:01000111; B:11100011; FLAG:01111110; ESC: 11100000

Show the bit sequence transmitted (in binary) for the four-character frame: A B ESC

FLAG when each of the following framing methods are used:

(a) Character count.

(b) Flag bytes with byte stuffing.

(c) Starting and ending flag bytes, with bit stuffing.

 

Solution:

 

a. 00000100 0100011111100011 11100000 01111110

b. 01111110 0100011111100011 11100000 11100000 11100000 01111110

01111110

c. 01111110 01000111110100011 111000000 011111010 01111110

An upper-layer packet is split into 10 frames, each of which has an 80 percent chance of arriving undamaged.

Q: An upper-layer packet is split into 10 frames, each of which has an 80 percent chance of arriving undamaged. If no error control is done by the data link protocol, how many times must the message be sent on average to get the entire thing through?

Solution:

First notice that no error checking is done by the data link protocol. What this means is that if an error occurs in a frame this information will not be known until all 10 frames have been transmitted and reassembled(the transport layer is doing some error control presumably, and will detect if there was an error in 1 or more frames and if so, request re-transmission). So in the case of this problem, we can't just repeatedly send the first frame until it gets through without error, then do the same for the second,etc. Instead, we must send all 10 frames. If they all get through without error we are done. Otherwise, we must send all 10again.
Because each frame has a probability of 0.8 of getting through correctly and errors can be considered independent events, the probability of the whole message getting through correctly on any given attempt is which is about 0.107 (or 10.7%). Call this value p.
Now notice that the probability of the message requiring i transmissions is .The reason is that if it takes exactly i transmissions, the first i-1 attempts must have failed(this happens with probability since the probability of a failed transmission is (1- probability of successful transmission) = (1-p). After these failed attempts,the ith attempt must succeed. This happens with probability p.
To compute the expected number of transmissions required(i.e.the average transmissions required) we weight all the possible transmissions required with their respective probabilities and then sum over all these possibilities. So the expected number of transmissions, E, is:

Notice that the last sum starts at i=0. This is fine since at i=0 =0, so we are just adding 0, something that doesn't change the value of the expression.
To evaluate this sum, we again use the trick of differentiating a series for which we already know the sum to get a form that is useful in the problem at hand.
It was proven in class that
Taking the derivative of both sides shows that .
Now, we just set r=1-p to get .Notice that we must have r<1 for the above equations to hold. But since r=1-p and ,r < 1 as needed.
So the answer is 1/0.107 or about 9.3 transmissions.
Now, we do the same problem, but take the probability of error-free transmission for a frame to be 0.99. In this case which is about 0.904 (quite a bit higher than the first part). The work we did in the first part still holds, so al lwe need to do is calculate which in this case is about 1.1.