1.1. Introduction

Network security is the branch of computer science that consists of protecting all components of a computer network in order to prevent unauthorized access, data stealing, misuse of a network connection, modification of data, etc. The aim of network security is to provide proactive defense methods and mechanisms to protect a network against internal and external threats.

1.2. Types of network security

We identify three categories of network security.

1.3. The main risks related to the logical security of the network

1.4. Exercises to test learning

ETL 1.–

1. 1. What security term refers to property or data that is valuable to an organization?
   1. a. A risk.
   2. b. A resource.
   3. c. A countermeasure.
   4. d. A vulnerability.
2. 2. Which of the following elements represents a physical security measure?
   1. a. The policy of changing security agents.
   2. b. The daily verification of equipment event logs.
   3. c. Implementing electronic locks.
   4. d. Putting in place access lists.
3. 3. Which of the following is a reason for using firewalls?
   1. a. Preventing unauthorized access of incoming or outgoing requests into a network.
   2. b. Preventing damage to a computer in case of fire.
   3. c. Facilitating the downloading of data from websites.
   4. d. Detecting and cleaning viruses on a computer.
4. 4. Which of the following respects confidentiality of information?
   1. a. Discussing confidential data over the telephone.
   2. b. Disclosing confidential information only to authorized persons.
   3. c. Downloading confidential information on a shared website.
   4. d. Sending confidential information to a colleague.
5. 5. Match the type of hacker to their description.

   Type of hacker	Description
   1. Carders	a. Individuals who use their computer skills for financial gain or to harm individuals or organizations
   2. Hacktivists	b. They usually contribute to the identification and repair of security weaknesses within a system.
   3. Phreakers	c. They chiefly attack smartcard systems in order to exploit their vulnerabilities.
   4. White Hat	d. Individuals who use their computer skills in order to bring about political or social change.
   5. Black Hat	e. People who make use of telephone networks to place calls for free.

6. 6. What kind of malicious program may be described as a software that attaches itself to another program in order to execute an undesirable function?
   1. a. Virus.
   2. b. Spyware.
   3. c. Trojan.
   4. d. Adware.
   5. e. Worm.
7. 7. What is the chief characteristic of worms?
   1. a. A worm can run independently.
   2. b. A worm must be activated by an event on the host system.
   3. c. A worm disguises itself as a legitimate software.
   4. d. Once installed on the host system, the worm does not replicate itself.
8. 8. Classify the security measures into physical, logical or administrative.

   Physical security	Logical security	Administrative security

   • - Defining the time of entry and exit from the computer room.
   • - Installing an incident protection system.
   • - Installing a firewall.
   • - Defining rules for an ACL.
   • - Recording all operations related to the handling of equipment.
   • - Installing surveillance cameras.
   • - Changing the location of an IPS system.
   • - Defining the length of encryption key.
   • - Mandating that all visitors wear badges.
   • - Putting in place the “least privilege” principle for accessing equipment.
9. 9. Which of these describes spam?
   1. a. Collecting information about a person or an organization without authorization.
   2. b. Carrying out an unauthorized action such as modifying or deleting files.
   3. c. Putting an unnecessary load on the system by copying files.
   4. d. Sending unwanted masses in bulk.
10. 10. Which of the following elements describes how a security breach must be reported?
    1. a. Using the telephone.
    2. b. Sending an email to the IT manager.
    3. c. Using any means of communication.
    4. d. Using the method given in the organization’s security policy.
11. 11. When you access a website, what icon in the address bar indicates that the site is secured?
    1. a. An arrow.
    2. b. A lock.
    3. c. A star.
    4. d. A shield.
12. 12. Which of the following may intercept and use your messages for its own purposes?
    1. a. The media.
    2. b. Governments.
    3. c. Advertising agencies.
    4. d. Crime networks.
    5. e. All of the above.
13. 13. What is the main method that is used to protect against malware?
    1. a. Using encrypted authentication technologies.
    2. b. Installing an antivirus software on all host devices.
    3. c. Blocking ICMP responses.
    4. d. Deploying intrusion prevention systems across the network.
14. 14. Which of the following describes a Trojan horse?
    1. a. Malware embedded in a seemingly legitimate executable program.
    2. b. Malware that sends extreme amounts of data in order to block a service.
    3. c. An electronic dictionary used to obtain the network administrator’s password.
    4. d. A software used to convince users that their system has been infected by viruses.

ETL 2.

1. 1. What simple countermeasure can be used to mitigate a “ping sweep” attack?
   1. a. Use encrypted authentication protocols.
   2. b. Installing an antivirus on the hosts.
   3. c. Deploying “anti-sniffer” software on all network devices.
   4. d. Blocking ICMP echo responses on all network devices.
2. 2. What network security countermeasures can be used to protect against DoS attacks? Choose two answers.
   1. a. Installing antivirus software.
   2. b. Putting in place IPS (intrusion protection systems).
   3. c. Installing applications to authenticate users.
   4. d. Installing anti-spoofing technology.
   5. e. Putting in place data encryption technology.
3. 3. How can you define a “ping sweep”?
   1. a. This is a network scanning technique that can discover available hosts available in an IP address range.
   2. b. This is an application that allows the capture of all network packets sent over a LAN.
   3. c. This is a technique that examines a range of port numbers (TCP or UDP) available on a LAN.
   4. d. This is a technique that can discover all the IP addresses available on a LAN using frame analysis.
4. 4. What are the two characteristics of DoS attacks? Choose two answers.
   1. a. They always precede access attacks.
   2. b. They try to compromise the availability of a network, host, or application.
   3. c. They are difficult to carry out and are only initiated by highly skilled attackers.
   4. d. They always use the ICMP protocol.
   5. e. They are easy to detect.
5. 5. What happens in a spoofing attack?
   1. a. An attacker modifies the data that transits over the network to access confidential information.
   2. b. An attacker sends large amounts of network traffic to a device to make it inaccessible to users.
   3. c. An attacker sends poorly formatted frames to a target device to cause it to malfunction.
   4. d. An attacker sends malicious code to steal all data stored on a device.
6. 6. What is the type of attack where an attacker uses an unauthorized access point to capture network traffic from a targeted user?
   1. a. Attacks on the approval relationship.
   2. b. Buffer overflow attack.
   3. c. “Man-in-the-middle” attack.
   4. d. DDoS attack
7. 7. This is a type of network security attack in which the intruder takes control of communication between two entities in order to use it for his benefit.
   1. a. Phishing.
   2. b. Buffer overflow.
   3. c. Pharming.
   4. d. Hijacking.
   5. e. SYN flood.
8. 8. What happens in a buffer overflow attack?
   1. a. An attacker redirects traffic from one website to another website.
   2. b. Attackers send multiple queries from many connected computers in different geographic regions to render a service unavailable.
   3. c. The attacker combines the characteristics of viruses, worms and other software to collect information about users.
   4. d. The attacker tries to write additional data in the saturated memory of an equipment.
9. 9. What is the risk of sharing too much information on social networking sites?
   1. a. Phishing.
   2. b. Buffer overflow.
   3. c. Pharming.
   4. d. Hijacking.
   5. e. Ransom.
10. 10. How many characters must be used to create a strong password?
    1. a. Eight characters.
    2. b. Sixteen characters.
    3. c. The maximum number of characters possible.
    4. d. The number of characters does not matter.
11. 11. Strong passwords can be difficult to remember, what can you do to avoid forgetting them?
    1. a. Use acronyms or phrases that are easy to remember.
    2. b. Develop a password strategy.
    3. c. Use password management software with encryption.
    4. d. All of the above.
12. 12. How long does it take for an attacker to detect a 10-character password?
    1. a. Less than an hour.
    2. b. Less than a week.
    3. c. Less than a month.
    4. d. It depends on many factors.
13. 13. An attacker uses the wireshark tool to discover usernames and administrative passwords. What kind of network attack is this?
    1. a. A “Man-in-the-middle” attack.
    2. b. A DoS attack.
    3. c. A reconnaissance attack.
    4. d. A close attack.