programs which can destroy or cause damage to data stored on a computer system and to the computer itself!

Virus program must be executed in order to dirty a computer system. Viruses can attach themselves to other programs in order to ensure that this happens.

A computer virus is a computer program that can copy itself and dirty a computer without permission or knowledge of the user.

Do not damage the original program or damage the hardware◦ May damage data files◦ “trash” firmware

But, some do For this reason most can be cleaned up with

anti-virus software.

User call for a legal program The virus code, having inserted itself in the

order of execution, executes in its place or in addition to the legal program.

The virus code terminates and returns control to the valid program

Turn off file sharing on the desktop or if you need some kind of file sharing, apply user-level security.

Don't open email attachments from unknown senders, especially files with an "exe", "vbs", "com" or "pif“.

All downloaded files from email should be saved to disk first and then virus scanned to determine if they are virus free before executing them.

Displaying unwanted messages

Loss of Data from a storage medium

Computers restarting unexpectedly

Unwanted generation of emails

Corrupt or delete data Disable the computer

by changing the operating system

Cause silly messages to be displayed or sounds to be produced

Worms operate differently to viruses

Worms can spread themselves to other computers without needing to be transferred as part of a host program.

The first time a user may notice the presence of a worm is when the computers memory UNEXPECTEDLY fills up

A worm is self-replicating software designed to spread through the network

◦ Can cause huge damage Access sensitive information Cause confusion by corrupting the sensitive information

Worm vs Virus A virus is code embedded in a file or program Worms are self-contained and may spread

autonomously

A Virus is a hateful program that spreads using a transmission technique that generally requires user involvement, and always have a hateful target

A worm on the other hand, has ability to self-spread, and may or may not have nasty purpose.

Capable of severely slow down the working of the internet

To unable us to build better defense systems

To unable possible good application The worst is yet to come!

Morris worm, 1988◦ Infected about 6,000 machines

10% of computers connected to the Internet

Code Red worm, July 16 2001

◦ Infected more than 500,000 servers

◦ Caused ~ $2.6 Billion in damages,

Mimili and Mimail.F are email worms cover themselves as an email from the PayPal on-line payment service and try to steal credit cards info.

This method of fraud is known phishing