Malicious code

DEFINITION

• 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

• 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.

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