Computer Security and its role

INTRODUCTION

The paper explores the role of Pass word, Anti virus and data  encryption in computer security.  It has been discussed that passwords is known to be ancient. Sentries would challenge those wishing to enter an area or approaching it to supply a password or watchword. Sentries would only allow a person or group to pass if they knew the password. In modern times, user names and passwords are commonly used by people during a log in process that controls access to protected computer operating systems, mobile phones, cable TV decoders, automated teller machines (ATMs), etc. Data encryption refers to mathematical calculations and algorithmic schemes that transform plaintext into cyphertext, a form that is non-readable to unauthorized parties. The recipient of an encrypted message uses a key which triggers the algorithm mechanism to decrypt the data, transforming it to the original plaintext version.

Lastly the paper discusses another important computer security software, computer virus which is a computer program that can copy itself and infect a computer without the permission or knowledge of the owner. The term “virus” is also commonly but erroneously used to refer to other types of malware, adware, and spyware programs that do not have the reproductive ability. A true virus can only spread from one computer to another (in some form of executable code) when its host is taken to the target computer; for instance because a user sent it over a network or the Internet, or carried it on a removable medium such as a floppy disk, CD, DVD, or USB drive.

MAIN BODY

A password is a secret word or string of characters that is used for authentication, to prove identity or gain access to a resource (Example: An access code is a type of password). The password must be kept secret from those not allowed access.

The use of passwords is known to be ancient. Sentries would challenge those wishing to enter an area or approaching it to supply a password or watchword. Sentries would only allow a person or group to pass if they knew the password. In modern times, user names and passwords are commonly used by people during a log in process that controls access to protected computer operating systems, mobile phones, cable TV decoders, automated teller machines (ATMs), etc. A typical computer user may require passwords for many purposes: logging in to computer accounts, retrieving e-mail from servers, accessing programs, databases, networks, web sites, and even reading the morning newspaper online.

Despite the name, there is no need for passwords to be actual words; indeed passwords which are not actual words may be harder to guess, a desirable property. Some passwords are formed from multiple words and may more accurately be called a passphrase. The term passcode is sometimes used when the secret information is purely numeric, such as the personal identification number (PIN) commonly used for ATM access. Passwords are generally short enough to be easily memorized and typed.

For the purposes of more compellingly authenticating the identity of one computing device to another, passwords have significant disadvantages (they may be stolen, spoofed, forgotten, etc.) over authentications systems relying on cryptographic protocols which are more difficult to circumvent. The original password concept has been proven to be insecure. There have been cases where passwords have been compromised without a users knowledge, through coersion, or because they were conned into revealing it. The core problem with legacy passwords is that it is very difficult or impossible for an administrator or a computer system to differentiate between a legitimate user and illegitimate user gaining access through the same password. Because of this inherent flaw in the original password system, Two Factor Authentication was invented.

A password is “something you know.” This information is understood to be known by a single individual. Two-factor authentication systems add in another factor, “something you have”, electronic card key, electronic token, dongle, fob or some other physical item you keep in a secure place when not in use. A common stand in replacement for this second factor when higher levels of security are needed is “something you are”. A biological fingerprint, retina pattern, person’s weight, specific vital signs or a combination of these items is used in place of the electronic device. The biological factor for authentication and authorization has been found to be unreliable, but not in that it permits those that should not be permitted when used properly, but because there is a tendency for it to deny legitimate users access due to sickness, physical body changes, or other physical impairments.

There are two common methods of authentication when users use electronic components for two-factor authentication, response-only, and challenge-response systems.

Response-only systems require a user to present your electronic device to an electronic reading system, or for you to enter data displayed on the electronic device without user input. The user must provide a username or pin that is not known to outsiders, and then enter specific credential data generated by the electronic device when prompted. In many cases, this mechanism returns the user back to a single factor authentication, where the user does not need to know something, but just posseses the item in question. An example of this is the standard electronic card key used to enter a facility or building perimiter. The user need not provide any other factor to prove their identity.

Challenge-response systems require the user to enter a specific passphrase or pin into the electronic device first, before the device responds with the proper access credentials data. This varient is always considered two-factor authentication, since the user must provide both “something they know” (the pin), and use “something they have” (the electronic device).

Both the response-only and challenge-response systems can be defeated if the user both reveals the private information they keep secret, such as their username or pin code, and the attacker takes ownership of the electronic device. Due to this weakness, the bioligcal factor was invented.

Biological factors have been in use for several decades, and have proven to be reliable and secure ways to prevent unauthorized users from gaining access to secure systems or environments, regardless of the privacy of their passwords used. Systems monitor fingerprints, eye retina patterns, weight, ambient temperature, and other biological signs to determine the authenticity of the user requesting access. Movies have been touting methods of defeating these systems by cutting off body parts, using retinal masks, or forcing legitimate users into bypassing the authentication mechanisms for the attacker. These are largely Hollywood schemes and rarely work in the real world. In most cases where this level of security is required, local or remote monitoring of entry points through cameras and security personnell is common. Deadlock portals, remote activated magnetically controlled entranceways, and visual idenfitication are the norm.

Many simple methods have been devised to defeat weakly designed biological factor systems, so be sure you thoroughly test the security measures you plan to put in place before implementation.

The easier a password is for the owner to remember generally means it will be easy for a hacker to guess. Passwords which are difficult to remember will reduce the security of a system because (a) users might need to write down or electronically store the password, (b) users will need frequent password resets and (c) users are more likely to re-use the same password. Similarly, the more stringent requirements for password strength, e.g. “have a mix of uppercase and lowercase letters and digits” or “change it monthly”, the greater the degree to which users will subvert the systemIn Jeff Yan et al. examine the effect of advice given to users about a good choice of password. They find that passwords based on thinking of a phrase and taking the first letter of each word, are just as memorable as naively selected passwords, and just as hard to crack as randomly generated passwords. Combining two unrelated words is another good method. Having a personally designed “algorithm” for generating obscure passwords is another good method.

However, asking users to remember a password consisting of a “mix of uppercase and lowercase characters” is like asking them to remember a sequence of bits: hard to remember, and only a little bit harder to crack (e.g. only 128 times harder to crack for 7-letter passwords, less if the user simply capitalises the first letter). Asking users to use “both letters and digits” will often lead to easy-to-guess substitutions such as ‘E’ –> ‘3’ and ‘I’ –> ‘1’, substitutions which are well known to crackers. Similarly typing the password one keyboard row higher is a common trick known to crackers.

Factors in the security of a password system

The security of a password-protected system depends on several factors. The overall system must, of course, be designed for sound security, with protection against computer viruses, man-in-the-middle attacks and the like. Physical security issues are also a concern, from deterring shoulder surfing to more sophisticated physical threats such as video cameras and keyboard sniffers. And, of course, passwords should be chosen so that they are hard for an attacker to guess and hard for an attacker to discover using any (and all) of the available automatic attack schemes. See password strength, computer security, and computer insecurity.

Effective access control provisions may force extreme measures on criminals seeking to acquire a password or biometric token. Less extreme measures include extortion, rubber hose cryptanalysis, side channel attack,

DATA ENCRYPTION

Data encryption refers to mathematical calculations and algorithmic schemes that transform plaintext into cyphertext, a form that is non-readable to unauthorized parties. The recipient of an encrypted message uses a key which triggers the algorithm mechanism to decrypt the data, transforming it to the original plaintext version.

Before the internet, data encryption was seldom used by the public as it was more of a military security tool. With the prevalence of online shopping, banking and other services, even basic home users are now aware of data encryption.

Today’s web browsers automatically encrypt text when making a connection to a secure server. This prevents intruders from listening in on private communications. Even if they are able to capture the message, encryption allows them to only view scrambled text or what many call unreadable gibberish. Upon arrival, the data is decrypted, allowing the intended recipient to view the message in its original form.

Types of Data Encryption

There are many different types of data encryption, but not all are reliable. In the beginning, 64-bit encryption was thought to be strong, but was proven wrong with the introduction of 128-bit solutions. AES (Advanced Encryption Standard) is the new standard and permits a maximum of 256-bits. In general, the stronger the computer, the better chance it has at breaking a data encryption scheme.

Data encryption schemes generally fall in two categories: symmetric and asymmetric. AES, DES and Blowfish use symmetric key algorithms. Each system uses a key which is shared among the sender and the recipient. This key has the ability to encrypt and decrypt the data. With asymmetric encryption such as Diffie-Hellman and RSA, a pair of keys is created and assigned: a private key and a public key. The public key can be known by anyone and used to encrypt data that will be sent to the owner. Once the message is encrypted, it can only be decrypted by the owner of the private key. Asymmetric encryption is said to be somewhat more secure than symmetric encryption as the private key is not to be shared.

Strong encryption like SSL (Secure Sockets Layer) and TLS (Transport Layer Security) will keep data private, but cannot always ensure security. Websites using this type of data encryption can be verified by checking the digital signature on their certificate, which should be validated by an approved CA (Certificate Authority).

Encryption with a variable key

A more advanced method is the use of simple encryption to encipher the virus. In this case, the virus consists of a small decrypting module and an encrypted copy of the virus code. If the virus is encrypted with a different key for each infected file, the only part of the virus that remains constant is the decrypting module, which would (for example) be appended to the end. In this case, a virus scanner cannot directly detect the virus using signatures, but it can still detect the decrypting module, which still makes indirect detection of the virus possible. Since these would be symmetric keys, stored on the infected host, it is in fact entirely possible to decrypt the final virus, but that probably isn’t required, since self-modifying code is such a rarity that it may be reason for virus scanners to at least flag the file as suspicious.

An old, but compact, encryption involves XORing each byte in a virus with a constant, so that the exclusive-or operation had only to be repeated for decryption. It is suspicious

COMPUTER VIRUS

A computer virus is a computer program that can copy itself and infect a computer without the permission or knowledge of the owner. The term “virus” is also commonly but erroneously used to refer to other types of malware, adware, and spyware programs that do not have the reproductive ability. A true virus can only spread from one computer to another (in some form of executable code) when its host is taken to the target computer; for instance because a user sent it over a network or the Internet, or carried it on a removable medium such as a floppy disk, CD, DVD, or USB drive. Viruses can increase their chances of spreading to other computers by infecting files on a network file system or a file system that is accessed by another computer. ( Fred Cohen) The term “computer virus” is sometimes used as a catch-all phrase to include all types of malware. Malware includes computer viruses, worms, trojan horses, most rootkits, spyware, dishonest adware, crimeware, and other malicious and unwanted software), including true viruses. Viruses are sometimes confused with computer worms and Trojan horses, which are technically different. A worm can exploit security vulnerabilities to spread itself to other computers without needing to be transferred as part of a host, and a Trojan horse is a program that appears harmless but has a hidden agenda. Worms

Methods to avoid detection

In order to avoid detection by users, some viruses employ different kinds of deception. Some old viruses, especially on the MS-DOS platform, make sure that the “last modified” date of a host file stays the same when the file is infected by the virus. This approach does not fool anti-virus software, however, especially those which maintain and date Cyclic redundancy checks on file changes.

Some viruses can infect files without increasing their sizes or damaging the files. They accomplish this by overwriting unused areas of executable files. These are called cavity viruses. For example the CIH virus, or Chernobyl Virus, infects Portable Executable files. Because those files have many empty gaps, the virus, which was 1 KB in length, did not add to the size of the file.

Some viruses try to avoid detection by killing the tasks associated with antivirus software before it can detect them.

As computers and operating systems grow larger and more complex, old hiding techniques need to be updated or replaced. Defending a computer against viruses may demand that a file system migrate towards detailed and explicit permission for every kind of file access. (T Matsumoto.)

Avoiding bait files and other undesirable hosts

A virus needs to infect hosts in order to spread further. In some cases, it might be a bad idea to infect a host program. For example, many anti-virus programs perform an integrity check of their own code. Infecting such programs will therefore increase the likelihood that the virus is detected. For this reason, some viruses are programmed not to infect programs that are known to be part of anti-virus software. Another type of host that viruses sometimes avoid is bait files. Bait files (or goat files) are files that are specially created by anti-virus software, or by anti-virus professionals themselves, to be infected by a virus. These files can be created for various reasons, all of which are related to the detection of the virus:

Anti-virus professionals can use bait files to take a sample of a virus (i.e. a copy of a program file that is infected by the virus). It is more practical to store and exchange a small, infected bait file, than to exchange a large application program that has been infected by the virus.

Anti-virus professionals can use bait files to study the behavior of a virus and evaluate detection methods. This is especially useful when the virus is polymorphic. In this case, the virus can be made to infect a large number of bait files. The infected files can be used to test whether a virus scanner detects all versions of the virus.

Some anti-virus software employs bait files that are accessed regularly. When these files are modified, the anti-virus software warns the user that a virus is probably active on the system.

Since bait files are used to detect the virus, or to make detection possible, a virus can benefit from not infecting them. Viruses typically do this by avoiding suspicious programs, such as small program files or programs that contain certain patterns of ‘garbage instructions’.

A related strategy to make baiting difficult is sparse infection. Sometimes, sparse infectors do not infect a host file that would be a suitable candidate for infection in other circumstances. For example, a virus can decide on a random basis whether to infect a file or not, or a virus can only infect host files on particular days of the week.

Stealth

Some viruses try to trick anti-virus software by intercepting its requests to the operating system. A virus can hide itself by intercepting the anti-virus software’s request to read the file and passing the request to the virus, instead of the OS. The virus can then return an uninfected version of the file to the anti-virus software, so that it seems that the file is “clean”. Modern anti-virus software employs various techniques to counter stealth mechanisms of viruses. The only completely reliable method to avoid stealth is to boot from a medium that is known to be clean.

Self-modification

Most modern antivirus programs try to find virus-patterns inside ordinary programs by scanning them for so-called virus signatures. A signature is a characteristic byte-pattern that is part of a certain virus or family of viruses. If a virus scanner finds such a pattern in a file, it notifies the user that the file is infected. The user can then delete, or (in some cases) “clean” or “heal” the infected file. Some viruses employ techniques that make detection by means of signatures difficult but probably not impossible. These viruses modify their code on each infection. That is, each infected file contains a different variant of the virus.

code that modifies itself, so the code to do the encryption/decryption may be part of the signature in many virus definitions.

Polymorphic code

Polymorphic code was the first technique that posed a serious threat to virus scanners. Just like regular encrypted viruses, a polymorphic virus infects files with an encrypted copy of itself, which is decoded by a decryption module. In the case of polymorphic viruses, however, this decryption module is also modified on each infection. A well-written polymorphic virus therefore has no parts which remain identical between infections, making it very difficult to detect directly using signatures. Anti-virus software can detect it by decrypting the viruses using an emulator, or by statistical pattern analysis of the encrypted virus body. To enable polymorphic code, the virus has to have a polymorphic engine (also called mutating engine or mutation engine) somewhere in its encrypted body. See Polymorphic code for technical detail on how such engines operateSome viruses employ polymorphic code in a way that constrains the mutation rate of the virus significantly. For example, a virus can be programmed to mutate only slightly over time, or it can be programmed to refrain from mutating when it infects a file on a computer that already contains copies of the virus. The advantage of using such slow polymorphic code is that it makes it more difficult for anti-virus professionals to obtain representative samples of the virus, because bait files that are infected in one run will typically contain identical or similar samples of the virus. This will make it more likely that the detection by the virus scanner will be unreliable, and that some instances of the virus may be able to avoid detection.

Metamorphic code

To avoid being detected by emulation, some viruses rewrite themselves completely each time they are to infect new executables. Viruses that use this technique are said to be metamorphic. To enable metamorphism, a metamorphic engine is needed. A metamorphic virus is usually very large and complex. For example, W32/Simile consisted of over 14000 lines of Assembly language code, 90% of which is part of the metamorphic engine.

Conclusion

As more users come to understand the internet’s open nature and the dangers of web surfing, applying data encryption to common communications such as emailing and instant messaging is likely to become more popular. Without this security mechanism, information transferred over the internet can be easily captured and viewed by anyone listening. This critical data can be compromised in a number of ways, especially when stored in servers that might change hands over the years. When considering how detrimental crimes like are identity theft are on the rise, data encryption is well worth pursuing.



Source by kabaso sydney Mupukwa

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