A computer virus is a computer program that is created to make and spread copies of itself. The program may however also be designed to have other effects on the systems it infects, ranging from the annoying to the disastrous. Virus attacks are growing rapidly these days. According to BusinessWeek, the 76,404 attacks reported in the first half of 2003 nearly match previous year's total number . As new antivirus tools are more powerful than before, the virus writers are getting a lot smarter with newer and creative ways to attack network systems. Let's first examine some common virus types: Basic Virus - a piece of software code that is developed to attack computers and network systems via email or Internet connections. It quickly replicates itself and gradually attaches to files, programs or the hard drive. Trojan Horses - This is a program that doesn't replicate when entering a system but can be effectively used to open 'back doors.' Trojan Horses allow hackers to take control over a particular system or to steal very important data. Worm - this type of virus is able to spread itself automatically over the network from one computer to the next. During a worm attack, users' computers get infected without even having to click open email attachment or any program, etc. Since it is very difficult to avoid the virus, your best defense is a powerful antivirus program. In order to fight with such viruses, the software vendors should focus on making their products more robust. This may ask for a trade-off between user-friendliness and security. In specific cases it may require line-by-line inspection, code retooling and even systems automation to defend the installed programs. 1. A computer virus is a computer program that is created to make and spread ______ of itself. A. programs B. virus C. copies D. files 2.Worm spread itself except by ______. A. network B. E-mail C. program D. hardware 3. Antivirus program can scan and virus. A. clean B. produce C. replicate D. make 4. Trojan Horses ______. A. quickly replicate itself and gradually attach to files, programs or the hard drive. B. infect the computer without even having to click open email attachment or any program. C. allow hackers to take control over a particular system or to steal very important data. D. avoid the virus to attack computer.