Narrator Listen to a part of a lecture in a computer class. what does the professor compare a computer virus to?

Good morning, everybody. Now last week we were looking at the positive effects that computers have had on our society. This week I’d like to talk about one of the negatives, computer viruses.
    OK. So what is a computer virus? Well, it is a software program that has been designed, tested and released by a human programmer with the single intention of corrupting and destroying useful programs. Put in simple terms, it’s a way of causing lots of trouble for ordinary people, just to be a nuisance! It’s known as a virus because, although it’s not a biological organism, it functions in a similar way, in that it seeks out a host; that is, a body, in which to live and multiply--your computer--with the end result of destroying that host.
    Let’s go back 50 years. In 1949 in the early days of computer technology, John Van Neumann presented the first model of a computer virus program in his paper "Theory and Organization of Complicated Automata". Soon after this paper was published, we find reference to a game known as "Core Wars". Core Wars was initially created for intellectual entertainment by three Americans working on large mainframe computers. Remember, in those days computers were the size of a couple of rooms. By the 1980s for the small sum of ＄2.00 postage anyone could get details on how to play "Core Wars" and very soon after, we see the emergence of a new pastime; one where people spent time creating programs that could escape the game and destroy other programs. In this way, the first computer viruses were born.
    Like their biological counterparts, computer viruses are picked up through casual habits. Virus programs are often intentionally placed within useful programs in the public domain, or they’re included in software which is not official--that is software that you might have acquired on tile black market, which, of course you don’t do!
    It seems quite hard to believe that anyone would go to this level of deceit to intentionally corrupt the data of others, but the rise in the number of computer software infections, and the amount of lost data that we are seeing these days, is proof that these virus programmers are going to extremes to do just that. They are going out of their way to create programs that hide inside legitimate software applications and cause all sorts of errors that the average end-user will then mistake for hardware failure---in other words they will think that the problem lies with their own computer.
    So, what can we do to combat these people? Well, the first thing is to realize that virus programmers succeed because people are not always careful about where they get their programs from. So, number one, be very careful. And I don’t just mean that you should be careful about the source of your software, you also need to take care with E-mails and avoid any messages which are suspicious-looking. For instance a message that says "I love you" or "Win ＄50". So the second golden rule is "avoid trouble". Now there are other things we can do to protect ourselves. We can try to find out exactly how the viruses work, how they accomplish their aims--in other words, we need to understand them.
    And, of course, there is a good selection of anti-virus software available on the market now as well as on the Internet to combat the virus plague, so another way of protecting ourselves and our computers is to be well prepared. And before I leave you, let me just say that if you ever run into one of those virus guys, tell them what you think of them!
Narrator Now get ready to answer some questions. You may use your notes to help you answer.
6. What is the talk mainly about?
7. What does the professor compare a computer virus to?
8. In the lecture, the professor describes the history of computer viruses. Indicate whether each of the following is a stage in history. Check the correct box for each phrase.
9.  What does the speaker find surprising?
Narrator Listen again to a part of the lecture. Then answer the question.
[Professor] or they’re included in software which is not official--that is software that you might have acquired on the black market, which, of course you don’t do!
10. What does the professor mean when he says thisΩ?
11. In the lecture, the professor talked about the different ways combating viruses. Indicate whether each of the following is proposed. Check the correct box for each phrase.