A01 chaf6542 06 se fm indd

Managing computer viruses

Computer viruses

 are a significant threat to company and personal information since it is 

estimated that there are now over 100,000 of them.

Types of virus

There are many different mechanisms by which computer viruses reproduce or ‘ self- 

 replicate’ and spread from one machine to another. The main different types are:

1 

 Boot‑  sector  virus. 

 Boot-  sector  viruses

 were most important when floppy disks were 

widely used.

2 

Worms. A 

worm

 is a small computer program that replicates itself and then transfers itself 

from one machine to the next. Since no human interaction is required, worms can spread 

very rapidly. For example, the ‘Code Red’ worm replicated itself over 250,000 times in just 

nine hours on 19 July 2001. In 2003, the ‘Slammer’ worm exploited a security loophole in 

the Microsoft SQL server database product and rapidly infected 75,000 machines. Each 

infected machine sent out so much traffic that many other servers failed also. This was one 

of the fastest spreading viruses of all time, as Figure 11.26 shows. In future it seems such 

worms will bring the Internet to a complete standstill.