CRYPTOGRAPHY AND CYBER SECURITY
UNIT-I
INTRODUCTION TO SECURITY
1.1 Computer Security Concepts
Computer security refers to protecting and securing computers and their related data, networks, software,
hardware from unauthorized access, misuse, theft, information loss, and other security issues. The Internet has
made our lives easier and has provided us with lots of advantages but it has also put our system’s security at risk
of being infected by a virus, of being hacked, information theft, damage to the system, and much more.
Technology is growing day by day and the entire world is in its grasp. We cannot imagine even a day without
electronic devices around us. With the use of this growing technology, invaders, hackers and thieves are trying to
harm our computer’s security for monetary gains, recognition purposes, ransom demands, bullying others,
invading into other businesses, organizations, etc. In order to protect our system from all these risks, computer
security is important.
Types of computer security
Computer security can be classified into four types:
1. Cyber Security: Cyber security means securing our computers, electronic devices, networks , programs,
systems from cyber attacks. Cyber attacks are those attacks that happen when our system is connected to the
Internet.
2. Information Security: Information security means protecting our system’s information from theft, illegal
use and piracy from unauthorized use. Information security has mainly three objectives: confidentiality, integrity,
and availability of information.
3. Application Security: Application security means securing our applications and data so that they don’t get
hacked and also the databases of the applications remain safe and private to the owner itself so that user’s data
remains confidential.
4. Network Security: Network security means securing a network and protecting the user’s information about
who is connected through that network. Over the network hackers steal, the packets of data through sniffing and
spoofing attacks, man in the middle attack, war driving, etc, and misuse the data for their benefits.
Types of cyber attack
1. Denial of service attack or DOS: A denial of service attack is a kind of cyber attack in which the attackers
disrupt the services of the particular network by sending infinite requests and temporary or permanently making
the network or machine resources unavailable to the intended audience.
2. Backdoor: In a backdoor attack, malware, trojan horse or virus gets installed in our system and start
affecting it’s security along with the main file. Consider an example: suppose you are installing free software
from a certain website on the Internet. Now, unknowingly, along with this software, a malicious file also gets
installed, and as soon as you execute the installed software that file’s malware gets affected and starts affecting
your computer security. This is known as a backdoor.
3.Eavesdropping: Eavesdropping refers to secretly listening to someone’s talk without their permission or
knowledge. Attackers try to steal, manipulate, modify, hack information or systems by passively listening to
network communication, knowing passwords etc. A physical example would be, suppose if you are talking to
another person of your organization and if a third person listens to your private talks then he/ she is said to
eavesdrop on your conversation. Similarly, your conversation on the internet maybe eavesdropped by attackers
listening to your private conversation by connecting to your network if it is insecure.
,4. Phishing: Phishing is pronounced as “fishing” and working functioning is also similar. While fishing, we
catch fish by luring them with bait. Similarly, in phishing, a user is tricked by the attacker who gains the trust of
the user or acts as if he is a genuine person and then steals the information by ditching. Not only attackers but
some certain websites that seem to be genuine, but actually they are fraud sites. These sites trick the users and
they end up giving their personal information such as login details or bank details or card number etc.
Phishing is of many types: Voice phishing, text phishing etc.
5. Spoofing: Spoofing is the act of masquerading as a valid entity through falsification of data(such as an IP
address or username), in order to gain access to information or resources that one is otherwise unauthorized to
obtain. Spoofing is of several types- email spoofing, IP address spoofing, MAC spoofing , biometric spoofing
etc.
6. Malware: Malware is made up of two terms: Malicious + Software = Malware. Malware intrudes into the
system and is designed to damage our computers. Different types of malware are adware, spyware, ransomware,
Trojan horse, etc.
7. Social engineering: Social engineering attack involves manipulating users psychologically and extracting
confidential or sensitive data from them by gaining their trust. The attacker generally exploits the trust of people
or users by relying on their cognitive basis.
8. Polymorphic Attacks: Poly means “many” and morph means “form”, polymorphic attacks are those in
which attacker adopts multiple forms and changes them so that they are not recognized easily. These kinds of
attacks are difficult to detect due to their changing forms.
Steps to ensure computer security
In order to protect our system from the above-mentioned attacks, users should take certain steps to ensure system
security:
1. Always keep your Operating System up to date. Keeping it up to date reduces the risk of their getting
attacked by malware, viruses, etc.
2. Always use a secure network connection. One should always connect to a secure network. Public wi-fi’s and
unsecured networks should be avoided as they are at risk of being attacked by the attacker.
3. Always install an Antivirus and keep it up to date. An antivirus is software that scans your PC against viruses
and isolates the infected file from other system files so that they don’t get affected. Also, we should try to go for
paid anti-viruses as they are more secure.
4. Enable firewall. A firewall is a system designed to prevent unauthorized access to/from a computer or even
to a private network of computers. A firewall can be either in hardware, software or a combination of both.
5. Use strong passwords. Always make strong passwords and different passwords for all social media accounts
so that they cannot be key logged, brute forced or detected easily using dictionary attacks. A strong password is
one that has 16 characters which are a combination of upper case and lower case alphabets, numbers and special
characters. Also, keep changing your passwords regularly.
6. Don’t trust someone easily. You never know someone’s intention, so don’t trust someone easily and end up
giving your personal information to them. You don’t know how they are going to use your information.
7. Keep your personal information hidden. Don’t post all your personal information on social media. You never
know who is spying on you. As in the real world, we try to avoid talking to strangers and sharing anything with
them. Similarly, social media also have people whom you don’t know and if you share all your information on it
you may end up troubling yourself.
8. Don’t download attachments that come along with e-mails unless and until you know that e-mail is from a
genuine source. Mostly, these attachments contain malware which, upon execution infect or harms your system.
9. Don’t purchase things online from anywhere. Make sure whenever you are shopping online you are doing so
from a well-known website. There are multiple fraud websites that may steal your card information as soon as
you checkout and you may get bankrupt by them.
, 10. Learn about computer security and ethics. You should be well aware of the safe computing and ethics of the
computing world. Gaining appropriate knowledge is always helpful in reducing cyber-crime.
11. If you are attacked, immediately inform the cyber cell so that they may take appropriate action and also
protect others from getting attacked by the same person. Don’t hesitate to complain just because you think
people may make your fun. 12. Don’t use pirated content. Often, people try to download pirated movies, videos
or web series in order to get them for free. These pirated content are at major risk of being infected with viruses,
worms, or malware, and when you download them you end up compromising your system security.
1.2 THE OSI SECURITY ARCHITECTURE
The security of an organization is the greatest concern of the people working at the organization. Safety and security
are the pillars of cyber technology. It is hard to imagine the cyber world without thinking about security. The
architecture of security is thus a very important aspect of the organization. The OSI (Open Systems
Interconnection) Security Architecture defines a systematic approach to providing security at each layer. It defines
security services and security mechanisms that can be used at each of the seven layers of the OSI model to provide
security for data transmitted over a network. These security services and mechanisms help to ensure the
confidentiality, integrity, and availability of the data. OSI architecture is internationally acceptable as it lays the
flow of providing safety in an organization. OSI Security Architecture focuses on these concepts:
• Security Attack:
• Security mechanism: A security mechanism is a means of protecting a system, network, or device against
unauthorized access, tampering, or other security threats.
• Security Service:
Classification of OSI Security Architecture
OSI Security Architecture is categorized into three broad categories namely Security Attacks, Security
mechanisms, and Security Services. We will discuss each in detail:
1. Security Attacks:
A security attack is an attempt by a person or entity to gain unauthorized access to disrupt or compromise the
security of a system, network, or device. These are defined as the actions that put at risk an organization’s safety.
They are further classified into 2 sub-categories:
A. Passive Attack:
Attacks in which a third-party intruder tries to access the message/ content/ data being shared by the sender and
receiver by keeping a close watch on the transmission or eave-dropping the transmission is called Passive Attacks.
These types of attacks involve the attacker observing or monitoring system, network, or device activity without
actively disrupting or altering it. Passive attacks are typically focused on gathering information or intelligence,
rather than causing damage or disruption.
Here, both the sender and receiver have no clue that their message/ data is accessible to some third-party intruder.
The message/ data transmitted remains in its usual form without any deviation from its usual behavior. This makes
passive attacks very risky as there is no information provided about the attack happening in the communication
UNIT-I
INTRODUCTION TO SECURITY
1.1 Computer Security Concepts
Computer security refers to protecting and securing computers and their related data, networks, software,
hardware from unauthorized access, misuse, theft, information loss, and other security issues. The Internet has
made our lives easier and has provided us with lots of advantages but it has also put our system’s security at risk
of being infected by a virus, of being hacked, information theft, damage to the system, and much more.
Technology is growing day by day and the entire world is in its grasp. We cannot imagine even a day without
electronic devices around us. With the use of this growing technology, invaders, hackers and thieves are trying to
harm our computer’s security for monetary gains, recognition purposes, ransom demands, bullying others,
invading into other businesses, organizations, etc. In order to protect our system from all these risks, computer
security is important.
Types of computer security
Computer security can be classified into four types:
1. Cyber Security: Cyber security means securing our computers, electronic devices, networks , programs,
systems from cyber attacks. Cyber attacks are those attacks that happen when our system is connected to the
Internet.
2. Information Security: Information security means protecting our system’s information from theft, illegal
use and piracy from unauthorized use. Information security has mainly three objectives: confidentiality, integrity,
and availability of information.
3. Application Security: Application security means securing our applications and data so that they don’t get
hacked and also the databases of the applications remain safe and private to the owner itself so that user’s data
remains confidential.
4. Network Security: Network security means securing a network and protecting the user’s information about
who is connected through that network. Over the network hackers steal, the packets of data through sniffing and
spoofing attacks, man in the middle attack, war driving, etc, and misuse the data for their benefits.
Types of cyber attack
1. Denial of service attack or DOS: A denial of service attack is a kind of cyber attack in which the attackers
disrupt the services of the particular network by sending infinite requests and temporary or permanently making
the network or machine resources unavailable to the intended audience.
2. Backdoor: In a backdoor attack, malware, trojan horse or virus gets installed in our system and start
affecting it’s security along with the main file. Consider an example: suppose you are installing free software
from a certain website on the Internet. Now, unknowingly, along with this software, a malicious file also gets
installed, and as soon as you execute the installed software that file’s malware gets affected and starts affecting
your computer security. This is known as a backdoor.
3.Eavesdropping: Eavesdropping refers to secretly listening to someone’s talk without their permission or
knowledge. Attackers try to steal, manipulate, modify, hack information or systems by passively listening to
network communication, knowing passwords etc. A physical example would be, suppose if you are talking to
another person of your organization and if a third person listens to your private talks then he/ she is said to
eavesdrop on your conversation. Similarly, your conversation on the internet maybe eavesdropped by attackers
listening to your private conversation by connecting to your network if it is insecure.
,4. Phishing: Phishing is pronounced as “fishing” and working functioning is also similar. While fishing, we
catch fish by luring them with bait. Similarly, in phishing, a user is tricked by the attacker who gains the trust of
the user or acts as if he is a genuine person and then steals the information by ditching. Not only attackers but
some certain websites that seem to be genuine, but actually they are fraud sites. These sites trick the users and
they end up giving their personal information such as login details or bank details or card number etc.
Phishing is of many types: Voice phishing, text phishing etc.
5. Spoofing: Spoofing is the act of masquerading as a valid entity through falsification of data(such as an IP
address or username), in order to gain access to information or resources that one is otherwise unauthorized to
obtain. Spoofing is of several types- email spoofing, IP address spoofing, MAC spoofing , biometric spoofing
etc.
6. Malware: Malware is made up of two terms: Malicious + Software = Malware. Malware intrudes into the
system and is designed to damage our computers. Different types of malware are adware, spyware, ransomware,
Trojan horse, etc.
7. Social engineering: Social engineering attack involves manipulating users psychologically and extracting
confidential or sensitive data from them by gaining their trust. The attacker generally exploits the trust of people
or users by relying on their cognitive basis.
8. Polymorphic Attacks: Poly means “many” and morph means “form”, polymorphic attacks are those in
which attacker adopts multiple forms and changes them so that they are not recognized easily. These kinds of
attacks are difficult to detect due to their changing forms.
Steps to ensure computer security
In order to protect our system from the above-mentioned attacks, users should take certain steps to ensure system
security:
1. Always keep your Operating System up to date. Keeping it up to date reduces the risk of their getting
attacked by malware, viruses, etc.
2. Always use a secure network connection. One should always connect to a secure network. Public wi-fi’s and
unsecured networks should be avoided as they are at risk of being attacked by the attacker.
3. Always install an Antivirus and keep it up to date. An antivirus is software that scans your PC against viruses
and isolates the infected file from other system files so that they don’t get affected. Also, we should try to go for
paid anti-viruses as they are more secure.
4. Enable firewall. A firewall is a system designed to prevent unauthorized access to/from a computer or even
to a private network of computers. A firewall can be either in hardware, software or a combination of both.
5. Use strong passwords. Always make strong passwords and different passwords for all social media accounts
so that they cannot be key logged, brute forced or detected easily using dictionary attacks. A strong password is
one that has 16 characters which are a combination of upper case and lower case alphabets, numbers and special
characters. Also, keep changing your passwords regularly.
6. Don’t trust someone easily. You never know someone’s intention, so don’t trust someone easily and end up
giving your personal information to them. You don’t know how they are going to use your information.
7. Keep your personal information hidden. Don’t post all your personal information on social media. You never
know who is spying on you. As in the real world, we try to avoid talking to strangers and sharing anything with
them. Similarly, social media also have people whom you don’t know and if you share all your information on it
you may end up troubling yourself.
8. Don’t download attachments that come along with e-mails unless and until you know that e-mail is from a
genuine source. Mostly, these attachments contain malware which, upon execution infect or harms your system.
9. Don’t purchase things online from anywhere. Make sure whenever you are shopping online you are doing so
from a well-known website. There are multiple fraud websites that may steal your card information as soon as
you checkout and you may get bankrupt by them.
, 10. Learn about computer security and ethics. You should be well aware of the safe computing and ethics of the
computing world. Gaining appropriate knowledge is always helpful in reducing cyber-crime.
11. If you are attacked, immediately inform the cyber cell so that they may take appropriate action and also
protect others from getting attacked by the same person. Don’t hesitate to complain just because you think
people may make your fun. 12. Don’t use pirated content. Often, people try to download pirated movies, videos
or web series in order to get them for free. These pirated content are at major risk of being infected with viruses,
worms, or malware, and when you download them you end up compromising your system security.
1.2 THE OSI SECURITY ARCHITECTURE
The security of an organization is the greatest concern of the people working at the organization. Safety and security
are the pillars of cyber technology. It is hard to imagine the cyber world without thinking about security. The
architecture of security is thus a very important aspect of the organization. The OSI (Open Systems
Interconnection) Security Architecture defines a systematic approach to providing security at each layer. It defines
security services and security mechanisms that can be used at each of the seven layers of the OSI model to provide
security for data transmitted over a network. These security services and mechanisms help to ensure the
confidentiality, integrity, and availability of the data. OSI architecture is internationally acceptable as it lays the
flow of providing safety in an organization. OSI Security Architecture focuses on these concepts:
• Security Attack:
• Security mechanism: A security mechanism is a means of protecting a system, network, or device against
unauthorized access, tampering, or other security threats.
• Security Service:
Classification of OSI Security Architecture
OSI Security Architecture is categorized into three broad categories namely Security Attacks, Security
mechanisms, and Security Services. We will discuss each in detail:
1. Security Attacks:
A security attack is an attempt by a person or entity to gain unauthorized access to disrupt or compromise the
security of a system, network, or device. These are defined as the actions that put at risk an organization’s safety.
They are further classified into 2 sub-categories:
A. Passive Attack:
Attacks in which a third-party intruder tries to access the message/ content/ data being shared by the sender and
receiver by keeping a close watch on the transmission or eave-dropping the transmission is called Passive Attacks.
These types of attacks involve the attacker observing or monitoring system, network, or device activity without
actively disrupting or altering it. Passive attacks are typically focused on gathering information or intelligence,
rather than causing damage or disruption.
Here, both the sender and receiver have no clue that their message/ data is accessible to some third-party intruder.
The message/ data transmitted remains in its usual form without any deviation from its usual behavior. This makes
passive attacks very risky as there is no information provided about the attack happening in the communication
