The continuous development of computer network system
brings both a great experience and convenience but new
security threats for users. Computer security problem generally
includes network system security and data security. Specifically, it refers to the reliability of network system, confidentiality, integrity and availability of data information in
the system. Network security problem exists through all the
layers of the computer network, and the network security
objective is to maintain the confidentiality, authenticity, integrity, dependability, availability and audit-ability of the network. This paper mainly aims to discuss about the basic
concepts,implementations of security mechanisms, Policies and latest threats of various systems that are upcoming today. Keywords
Goals, Cryptography, Cryptanalysis, Access Control Lists, Mechanisms, Bell-LaPadula, Biba. 1. INTRODUCTION
Computer security should be seen as a basic management task. It is an extension of the duty to protect the organization’s assets against misuse or loss. Also, the information stored and processed by computers is the most significant asset of most organizations. (Some prefer to
the use the term information security to describe the process of
protecting computing. It plays a major role in ensuring an
organization’s ability to survive as what the law calls a going
concern. Increasingly, maintaining this process will involve
ensuring that the organization is complying with relevant statutory and regulatory agency requirements.)
Information is inevitable in all kinds of entrepreneurial activities, and must be therefore protected as assets. Information security may be assured in various ways, including related policies, processes, procedures, organizational structures, software programs and hardware
equipment able to eliminate many sources of safety
jeopardizing such as espionage, computer fraud and deceit, sabotage, vandalism, fire or water. Computer Security is the protection of computing systems and
the data that they store or access. How many attacks to computers on campus do you think take place everyday?
? Thousands of attacks per minute bombard our campus network. ? An unprotected computer can become infected or compromised within a few seconds after it is connected
to the network. ? A compromised computer is a hazard to everyone else, too – not just to you. 1
2.1 Goals of Security: Computer security rests on Confidentiality, Integrity and Availability that is CIA. The
interpretation of these aspects vary, as do the contexts in which they arise. The interpretation of aspect in a given
environment is dictated by the needs of the individuals, customs and laws of particular organizations. But we can
define it in a general way as follows- 1. Confidentiality
Confidentiality is the concealment of information or resources. The need of keeping information secret arises from the use of computer in sensitive fields such as government. Ex- Military,banks. 2. Integrity
Integrity refers to the trustworthiness of data or resources and
it usually phrased in terms of preventing improper or unauthorized change. Integrity includes data integrity(Content
information) and origin integrity(the source of data often
called authentication). 3. Availability
Availability refers to the ability to use the information or
resource desired. Computer security professionals usually address three
common challenges to availability: Denial of service (DoS)
due to intentional attacks or because of undiscovered flaws in
implementation (for example, a program written by a programmer who is unaware of a flaw that could crash the program if a certain unexpected input is encountered).Loss of
information system capabilities because of natural disasters
(fires, floods, storms, or earthquakes) or human actions
(bombs or strikes). And Equipment failures during normal use.2
2.2 Threats: A threat, in the context of computer security, refers to anything that has the potential to cause serious harm
to a computer system. A threat is something that may or may
not happen, but has the potential to cause serious damage. Threats can lead to attacks on computer systems, networks and more. 2.3 Cryptography: Cryptography means secret writing. Basically writing text in secret form such that it’s not understandable to attackers. Cryptanalysis is the breaking of codes. The basic component of cryptography is Cryptosystem. 2.4 Policies: A. Security Policies- A security model is a model that represents a particular policy
or set of policies. A model abstracts details relevant for analysis. Analyses rarely discuss particular policies; they
usually focus on specific characteristics of policies, because many policies exhibit these characteristics; and the more policies with those characteristics, the more useful the analysis. By the HRU result, no single nontrivial analysis can cover all
policies, but restricting the class of security policies
sufficiently allows meaningful analysis of that class of
B.Confidentiality Policies- Confidentiality is one of the factors of privacy, an issue
recognized in the laws of many government entities (such as
the Privacy Act of the United States and similar legislation in Sweden). Aside from constraining what information a government entity can legally obtain from individuals, such
acts place constraints on the disclosure and use of that
information. Unauthorized disclosure can result in penalties
that include jail or fines; also, such disclosure undermines the
authority and respect that individuals have for the government and inhibits them from disclosing that type of information to
the agencies so compromised. I. The Bell – LaPadula Model- The simplest type of confidentiality classification is a set of security clearances arranged in a linear (total) ordering . These
clearances represent sensitivity levels. The higher the security
clearance, the more sensitive the information (and the greater
the need to keep it confidential). A subject has a security
clearance. In the figure, Claire’s security clearance is C (for CONFIDENTIAL), and Thomas’ is TS (for TOP SECRET). An
object has a security classification; the security classification of
the electronic mail files is S (for SECRET), and that of the
telephone list files is UC (for UNCLASSIFIED). (When we
refer to both subject clearances and object classifications, we use the term “classification.”) The goal of the Bell-LaPadula
security model is to prevent read access to objects at a security
classification higher than the subject’s clearance. The Bell- LaPadula security model combines mandatory and
discretionary access controls. In what follows, “S has discretionary read (write) access to O” means that the access control matrix entry for S and O corresponding to the discretionary access control component contains a read (write)
right. In other words, were the mandatory controls not present, S would be able to read (write) O. 3
Figure 1: Classification of Bell – LaPadula Model3
C. Integrity Policies 1. Biba Integrity ModelIn
1977, Biba studied the nature of the integrity of systems. In
his model, a system consists of a set S of subjects, a set O of objects, and a set I of integrity levels.1 The levels are ordered. The relation ? ? I × I holds when the second integrity level either dominates or is the same as the first. The function i:S
? O?I returns the integrity level of an object or a subject.3
2. Clark Wilsoon Integrity Models
In 1987, David Clark and David Wilson developed an
integrity model radically different from previous models. This model uses transactions as the basic operation, which models many commercial systems more realistically than previous models. One main concern of a commercial environment, as discussed above, is the integrity of the data in the system and
of the actions performed on that data. The data is said to be in
a consistent state (or consistent) if it satisfies given properties. For example, let D be the amount of money deposited so far
today, W the amount of money withdrawn so far today, YB
the amount of money in all accounts at the end of yesterday, and TB the amount of money in all accounts so far today. Then the consistency property is D + YB – W = TB Before
and after each action, the consistency conditions must hold. A
well-formed transaction is a series of operations that transition
the system from one consistent state to another consistent state. For example, if a depositor transfers money from one account
to another, the transaction is the transfer; two operations, the deduction from the first account and the addition to the second
account, make up this transaction. Each operation may leave
the data in an inconsistent state, but the well-formed
transaction must preserve consistency. 3
Implementing Computer security techniques fall under
following types: 3.1 Cryptography- The art or science encompassing the principles and methods of
transforming an intelligible message into one that is unintelligible, and then re-transforming that message back to
its original form.4
The classical Cryptosystem consists of following types- 1. Transposition Cipher- A transposition cipher is a method
of encryption by which the positions held by units of plain text
(which are commonly characters or groups of characters) are
shifted according to a regular system, so that the cipher text constitutes a permutation of the plain text. 2. Substitution cipher- A substitution cipher is a method of encrypting by which units of plain text are replaced with
cipher text, according to a fixed system; the “units” may be
single letters (the most common), pairs of letters, triplets of
letters, mixtures of the above, and so forth. 3. Vigenère cipher- The Vigenère cipher is a method of encrypting alphabetic text by using a series of interwoven Caesar ciphers based on the letters of a keyword. 4. One time pad- In this technique, a plain text is paired with a
random secret key (also referred to as a one-time pad). Then, each bit or character of the plain text is encrypted by
combining it with the corresponding bit or character from the pad using modular addition. If the key is truly random, is at
least as long as the plain text, is never reused in whole or in
part, and is kept completely secret, then the
resulting ciphertext will be impossible to decrypt or break. 5. Public key Cryptosystem- PKC works in way illustrated in following figure.
Figure 2: Working of Public key Cryptosystem5
There are 2 types of PKCs as follows: a Diffie-Hellman
It was the first PKC proposed. It is based on Discrete Logarithm Problem. b. RSA
It is an exponential cipher. This type of cipher is even
used today. (Note: Algorithms to be followed in section)
Protecting cryptographic keys may sound simple: just put the key into file and use operating system access control mechanisms to protect it. But as we know in a number of ways these mechanisms can be compromised leading to keys getting invaded. In this section we discuss some mechanisms
to prevent keys. Following are some key management
techniques. 1. Kerberos Kerberos provides a centralized authentication server whose
function is to authenticate users to servers and servers to users. Unlike most other authentication schemes described in this book, Kerberos relies exclusively on symmetric encryption, making no use of public-key encryption.
Figure 3: Working of Kerberos6
2. Key escrow (also known as a “fair” Cryptosystem) is an
arrangement in which the keys needed to decrypt encrypted
data are held in escrow so that, under certain circumstances, an authorized third party may gain access to those keys. Key
escrow is a data security measure in which a cryptographic key is entrusted to a third party (i.e., kept in escrow). Under normal circumstances, the key is not released to someone other than the sender or receiver without proper authorization. For the above key management techniques, various authentication techniques are used for verifying the user authenticity. Techniques include following: 1. Passwords 2. Challenge-Response (OTP)
3. Biometric
a. Fingerprint
b. Face recognition
c. Retina Scan
d. Face scan
e. Voice recognition A combination of above three techniques is used for authenticity of users. Access Control is a set of controls to restrict access to certain
resources. If we think about it, access controls are everywhere
around us. A door to your room, the guards allowing you to
enter the office building on seeing your access card, swiping
your card and scanning your fingers on the biometric system, a queue for food at the canteen or entering your credentials to
access FB, all are examples of various types of access control. Here we focus only on the logical Access Control mechanisms. 1. Discretionary Access Control (DAC)
Discretionary access controls base access rights on the identity
of the subject and the identity of the object involved. Identity
is the key; the owner of the object constrains who can access it
by allowing only particular subjects to have access. The owner states the constraint in terms of the identity of the subject, or
the owner of the subject.
EXAMPLE: Suppose a child keeps a diary. The child controls access to the diary, because she can allow someone to read it
(grant read access) or not allow someone to read it (deny read
access). The child allows her mother to read it, but no one else. This is a discretionary access control because access to the diary is based on the identity of the subject (mom) requesting
read access to the object (the diary). 2. Mandatory Access Control (MAC)
When a system mechanism controls access to an object and an
individual user cannot alter that access, the control is a mandatory access control (MAC), occasionally called a rule- based access control. The operating system enforces mandatory access controls. Neither the subject nor the owner of the object can determine whether access is granted. Typically, the system mechanism will check information
associated with both the subject and the object to determine whether the subject should access the object. Rules describe
the conditions under which access is allowed. EXAMPLE: The law allows a court to access driving records without the owners’ permission. This is a mandatory control, because the owner of the record has no control over the
court’s accessing the information. 3. Role Based Access Control (RBAC)
RBAC is the buzzword across enterprises today. In this model
the access to a resource is governed based on the role that the
subject holds within an organization. RBAC is also known as non-discretionary Access Control because the user inherits privileges that are tied to his role. The user does not have a
control over the role that he will be assigned. Each of the
above Access Models has its own advantages and
disadvantages. The selection of the appropriate Access Model
by an organization should be done by considering various
factors such as type of business, no of users, organization’s
security policy etc. 4. Access Control lists(ACLs)
An obvious variant of the access control matrix is to store
each column with the object it represents. Thus, each object
has associated with it a set of pairs, with each pair containing
a subject and a set of rights. The named subject can access the
associated object using any of those rights. More formally: Let S be the set of subjects, and R the set of rights, of a
system. An access control list (ACL) l is a set of pairs l = { (s, r) : s ? S, r ? R }. Let acl be a function that determines the
access control list l associated with a particular object o. The
interpretation of the access control list acl(o) = { (si , ri ) : 1 ?
i ? n } is that subject si may access o using any right in ri . 5. STEPWISE EXPLANATION OF
1. Diffie-Hellman
Figure 4: Deffie – Hellman Steps7
2. RSA
* Generating Public key: Select two prime no’s. Suppose P = 53 and Q = 59. Now First part of the Public key : n = P*Q = 3127. We also need a small exponent say e : But e Must be An integer. Not be a factor of n. 1 < e < ?(n) ?(n) is discussed below, Let us now consider it to be equal to 3. * Generating Private Key : We need to calculate ?(n) : Such that ?(n) = (P-1)(Q-1) so, ?(n) = 3016 Now calculate Private Key, d : d = (k*?(n) + 1) / e for some integer k For k = 2, value of d is 2011. Now we are ready with our – Public Key ( n = 3127 and e = 3) and Private Key(d = 2011) *Encryption: Now we will encrypt "HI" : Convert letters to numbers : H = 8 and I = 9 Thus Encrypted Data c = 89e mod n. Thus our Encrypted Data comes out to be 1394 Now we will decrypt 1349 : Decrypted Data = cd mod n. Thus our Encrypted Data comes out to be 89 8 = H and I = 9 i.e. "HI". 7 6. ALGORITHM COMPARISON No. Parameters RSA Diffie-Hellman 1. Encryption Cheaper Expensive Cost Public key Public key is Public key is 2. smaller to encoding bigger to encode. encode. Less More Robust(1024 3. Strength robust(1024 bits). bits). Depends on Depends on 4. Security difficulty of difficulty of Integer Discrete Factorization. Logarithm. Authenticati Performs to Performs for both 5. Sender and on only sender. Receiver. 6. Key Extremely Easier. generation difficult. Type of Common Man in the middle 7. attacks modulus and attack. possible cycle attack. Table 1: Comparison of RSA and Diffie-Hellman8 7. LATEST RISKY THREATS A popular technique used by website operators to observe the keystrokes, mouse movements and scrolling behavior of visitors on Web pages is fraught with risk, according to researchers at Princeton's Center for Information Technology Policy. The technique offered by a number of service providers uses scripts to capture the activity of a visitor on a Web page, store it on the provider's servers, and play it back on demand for a website's operators. The idea behind the practice is to give operators insights into how users are interacting with their websites and to identify broken and confusing pages. Let us see a few threats that are upcoming since the past few years: 1. Peeping Scripts However, the extent of data collected by the scripts far exceeds user expectations, according to researchers Steven Englehardt, Gunes Acar and Arvind Narayanan. Text typed into forms is collected before a user submits the form, and precise mouse movements are saved -- all without any visual indication to the user, they noted in an online post. What's more, the data can't be reasonably expected to be kept anonymous. "In fact, some companies allow publishers to explicitly link recordings to a user's real identity," wrote the team. "Unlike typical analytics services that provide aggregate statistics, these scripts are intended for the recording and playback of individual browsing sessions, as if someone is looking over your shoulder." That means that whether a visitor completes a form and submits it to the website or not, any information keyed in at the website can be seen by the operator.9 2. chaiOS Software developer Abraham Masri claimed to have found the bug, called "chaiOS,"The so-called "text bomb" typically causes an iPhone to crash and, in some cases, restart. Sending a message which contains the link to Masri's code would be all it takes to activate the bug — even if the recipient did not click on the link. Meanwhile, on a Mac computer, the security flaw was found to crash the Safari browser, as well as causing other slowdowns.10 3. Ransomware Holding organizations data for ransom has surged up in recent times at a phenomenal rate. And SonicWall reports that ransomware attempts have swelled up from 2.8 million in 2015 to 638 million last year. The company's report also confirms that as much as $209 million was paid in 1Q of 2016 alone. Thus the amount paid says a lot about malware.11 4. Internet of things Botnets In late 2016, when an enormous DDoS attack was launched on DNS Service provider called DYN, the attack proved that many service providers were ill-equipped to deal with the scope of the latest cyber attacks. Mirai Botnet was found to be the culprit and this instance shocked the entire business community which otherwise thought that security in IoT devices was just secondary. So, IoT botnets are now standing second on the threats list. And Gartner expects that around 8.4 billion of things will get connected to the Internet in this year- perhaps a lot of trouble will be in store in future.11 5. Phishing and whaling attacks 'Phishing' is a concept where hackers send fraudulent emails from trusted accounts to target businesses through individual staff members. When an innocent staff member clicks on the email, then attachment which is tagged to the email starts functioning releasing a malware capable of stealing data. 'Whaling' takes the above said cyber attack strategy to next level by targeting high worth individuals, often CIOs or CEOs of a firm. FBI has warned all corporates operating in and out of United States about this scam and confirmed that hackers have succeeded in making $3 million from such fraudulent transactions last year.1 6. Business Process Compromise Attacks Trend Micro has described this concept of cyber attack as a relatively new phenomenon where hackers are using techniques to manipulate the day to day operations of a business in their favor. For instance, in the year 2013 drug traffickers from South America managed to intercept the network of an Antwerp to track the movement and location of containers. This helped the traffickers to retrieve the cargo at a secluded place before the naval police tried to arbitrate their operations. So, in this case, hackers were utilized to compromise the business process of a government firm to evade law enforcement forces and for financial gains. 7. Machine Learning enabled attacks It looks like the technology of Artificial Intelligence seems to be serving both the good and bad people. According to a recent Intel Security report, machine learning is being used to launch social engineering attacks. Like, if hackers gain access to publicly available data, they can use complex analysis tools to pick targets more precisely and with a greater level of success. For example, in the UK, hackers are gaining access to databases related to tax filing to launch ransomware related attacks on individuals who have filed for the highest IT returns. This proves that the data available on public platforms can be used to launch attacks on individuals for minting money. 7. CONCLUSION Statistics and a lot of research study shoes that data theft and abuse are becoming a profitable business worldwide. Perfect computer systems pose a significant barrier to illegal activities, yet there is always a chance to hack and misuse a system. Organizations such as ISO, IEC, OECD and IEE have therefore prepared a wide range of standards, guidelines and instructions on how to implement information security management, e.g.: a) ISO/IEC Guide 73: 2002 Risk management. Vocabulary. Guidelines for use in standards. b) ISO/IEC 13335-1: 2004 Information technology security techniques. c) ISO/IEC 27002: 2007 Information technology. Security techniques. Code of practice for information security management. d) Management of information and communications technology security. Part 1: Concepts and models for information and communications technology security management. e) ISO/IEC 15408-1: 1999 Information technology. Security techniques. Evaluation criteria for IT security. Part 1: Introduction and general model. f) ISO/IEC 15489-1: 2001 Information and documentation. Records management. Part 1: General. g) OECD Guidelines for the Security of Information Systems and Networks. Towards a Culture of Security. 2002 ISO/IEC TR 18044 Information Technology. h) Security Techniques. Information security incident management. 12 


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