Computer security

➧Other intruders indicate some evidence of their presence either by leaving a message or ➧by deliberately altering or damaging data.
➧Any illegal act involving a computer generally is referred to as a computer crime.
➧Cybercrime refers to online or Internet-based illegal acts.
➧Software used by cybercriminals sometimes is called crimeware.

• Perpetrators of cybercrime and other intrusions fall into seven basic categories:
• Hacker, refers to someone who accesses a computer or network illegally. Some hackers claim the intent of their security breaches is to improve security.
• Cracker also is someone who accesses a computer or network illegally but has the intent of. destroying data, stealing information, or other malicious action
• Script kiddie has the same intent as a cracker but does not have the technical skills and knowledge. Often use prewritten hacking and cracking programs to break into computers.
• Corporate spies have excellent computer and networking skills.

ühired to break into a specific computer and steal its proprietary data and information.

üto help identify security risks in their own organization.

• Unethical employees may break into their employers’ computers for a variety of reasons:

üwant to exploit a security weakness,

üseek financial gains from selling confidential information

üdisgruntled employees may want revenge.

• Cyber extortionist is someone who uses e-mail as a medium for extortion.

üThey will send an organization a threatening e-mail message indicatingthey will expose confidential information if they are not paid a sum of money.

• Cyberterrorist is someone who uses the Internet or network to destroy or damage computers for political reasons. They might targets:

üthe nation’s air traffic control system,

üelectricity-generating companies,

üa telecommunications infrastructure.

Malicious code

➧Malicious code is code causing damage to a computer or system. It is code not easily or solely           controlled through the use of anti-virus tools.
➧Malicious code can either activate itself or be like a virus requiring user to perform an action, such      as clicking on something or opening an email attachment.

Computer Virus
Definition : A computer virus is a potentially damaging computer program that affects or infects, a computer negatively by altering the way the computer works without the user’s knowledge or permission.
➧A computer virus attaches itself to a program or file enabling it to spread from one                 computer to another, leaving infections as it travels
➧It may damage files and system software, including the operating system
➧Almost all viruses are attached to an executable file.
➧The virus may exist on your computer but it actually cannot infect your computer unless         you run or open the malicious program.
➧A computer virus by sharing infecting files or sending emails with viruses as attachments in   the email.Even such a simple virus is dangerous because it will quickly use all available       memory and bring the system to a halt.
Examples: Melissa, Tequila, Cascade, Invader  

Worm
➧A worm is a program that copies itself repeatedly.
➧For example in memory or on a network, using up resources and possibly shutting down      the computer or network.
➧Worms spread from computer to computer, but unlike a virus, it has the capability to travel   without any human action
➧A worm takes advantage of file or information transport features on your system, which is     what allows it to travel unaided.
➧The biggest danger with a worm is its capability to replicate itself on your system.
➧It will causing Web servers, network servers and individual computers to stop responding.

Examples: Jerusalem, Sobig,   Nimda, Morris Worm

Differentiate between worms and virus
Enable visualization to see the difference between the two.














Trojan Horse
➧A program that hides within or looks like a legitimate program. It does not replicate itself to   other computers.
➧At first glance will appear to be useful software but will actually do damage once installed     or run on your computer.
➧Examples: It can change your desktop, adding silly active desktop icons or they can cause   serious damage by deleting files and destroying information on your system.
Examples: Netbus, Back Orifice, Subseven, Beast 

Differences of Malicious code












Unauthorized access & use
Unauthorized accesss

• The use of a computer or network without permission.

Unauthorized use 

• The use of a computer or its data for unapproved or possibly illegal activities

To help prevent unauthorized access and use, they should have a written acceptable use policy (AUP) that outlines the computer activities for which the computer and network may and may not be used.An access control is a security measure that defines who can access a computer, when they can access it, and what actions they can take while accessing the computer.Many systems implement access controls using a two-phase process called identification and authentication.Identification verifies that an individual is a valid user.

Authentication verifies that the individual is the person he or she claims to be.Three methods of identification and authentication include user names and passwords, possessed objects, and bio metric devices.A user name or user ID (identification), is a unique combination of characters, such as letters of the alphabet or numbers, that identifies one specific user.A password is a private combination of characters associated with the user name that allows access to certain computer resources.

Most multi user (networked) operating systems require that users correctly enter a user name and a password before they can access the data, information and programs stored on a computer or network.

A possessed object is any item that you must carry to gain access to a computer or computer facility. Examples of possessed objects are badges, cards, smart cards and keys. The card you use in an automated teller machine (ATM) is a possessed object that allows access to your bank account. Possessed objects often are used in combination with personal identification numbers. 

A personal identification number (PIN) is a numeric password, either assigned by a company or selected by a user. A biometric device authenticates a person’s identity by translating a personal characteristic, such as a fingerprint into a digital code.

Hardware Theft

➤Hardware theft is the act of stealing computer equipment.

➤Hardware vandalism is the act of defacing or destroying computer equipment.

➤Companies, schools, and other organizations that house many computers, however, are       at risk of hardware theft.

➤Safeguards against Hardware Theft and Vandalism:

• physical access controls, such as locked doors and windows
• install alarm systems in their buildings
• physical security devices such as cables that lock the equipment to a desk.

Software Theft

➤Software theft occurs when someone:

• Steals software media
• Intentionally erases programs
• Illegally copies a program
• Illegally registers and/or activates a program.

➤Steals software media involves a perpetrator physically stealing the media that contain         the software or the hardware that contains the media.

➤Intentionally erases programs can occur when a programmer is terminated from, or stops     working for a company.

➤Although the programs are company property, some dishonest programmers intentionally     remove or disable the  programs they have written from company computers.

➤Illegally copies a program occurs when software is stolen from software manufacturers.

➤This type of theft, called piracy, is by far the most common form of software theft.

➤Illegally registers and/or activates a program involves users 

➤illegally obtaining registration numbers and/or activation codes.

➤A program called a keygen, short for key generator, creates software registration numbers    and sometimes activation codes.

➤Some individuals create and post keygens so that users can install software without              legally purchasing it

Safeguards against Software Theft

➤To protect software media from being stolen, owners should keep original software boxes      and media in a secure location, out of sight of prying eyes.

➤All computer users should back up their files and disks regularly.

➤To protect themselves from software piracy, software manufacturers issue users license         agreements.

Information Theft

➤Information theft occurs when someone steals personal or confidential information.

➤If stolen, the loss of information can cause as much damage as (if not more than)                  hardware or software theft.

➤An unethical company executive may steal or buy stolen information to learn about a             competitor.

➤A corrupt individual may steal credit card numbers to make fraudulent purchases.

Safeguards against Information Theft

➤Protecting information on computers located on an organization’s premises.

➤To protect information on the internet and networks, organizations and individuals use a         variety of encryption techniques.

➤Encryption is a process of converting readable data into unreadable characters to prevent     unauthorized access.

System Failure

➤A system failure is the prolonged malfunction of a computer

➤Can cause loss of hardware, software, data, or information.

➤These include aging hardware; natural disasters such as fires, floods, or hurricanes;             random events such as electrical power  problems; and even errors in computer                   programs.

➤Electrical power variations can cause loss of data and loss of equipment.

➤If the computer equipment is networked, a single power disturbance can damage multiple    systems.

➤Electrical disturbances include noise (any unwanted signal), undervoltages (electrical             supply drops), and overvoltages (incoming electrical power increases).

Safeguards against System failure

➤To protect against electrical power variations, use a surge protector.

➤A surge protector, also called a surge suppressor, uses special electrical components to      smooth out minor noise, provide a stable current flow, and keep an overvoltage from              reaching the computer and other electronic equipment.