計(jì)算機(jī)專業(yè)畢業(yè)論文外文翻譯--計(jì)算機(jī)病毒介紹

1、<p><b>　　一、英文原文</b></p><p>　　Virus Introduction</p><p>　　Viruses will cause much confusion. Even some virus “experts” will misinform the cause of the virus. Let's define wha

2、t we mean by virus.</p><p>　　A virus is a program that reproduces its own code by attaching itself to other executable files, so the virus code is executed when the infected executable file is executed. Here

3、, the program (COM or EXE file) refers to an executable file. To attach might mean physically adding to the end of a file, inserting into the middle of a file, or simply placing a pointer to a different location on the d

4、isk somewhere where the virus can find it.</p><p>　　Most viruses place self-replicating codes in other programs, so that when those other programs are executed, even more programs are "infected" wi

5、th the self-replicating codes. These self-replicating codes, when caused by some event, may do a potentially harmful act to your computer.</p><p>　　The macro portion of a data file maybe much more critical (

6、e.g., a Microsoft Word document), but less obvious. More recently, scripts written for Internet web sites and/or included in E-mail can also be executed and infected. Similar to viruses, you can also find malicious codes

7、 in Trojan Horses, worms, and logic bombs.</p><p>　　Virus Behavior－Infection Phase</p><p>　　Viruses have many different forms, but they all potentially have two phases to their execution: the in

8、fection phase and the attack phase. Now we firstly discuss the infection phase.</p><p>　　When the virus executes it can infect other programs. Some viruses infect other programs each time they are executed;

9、other viruses infect only upon a certain cause. This cause could be anything, a day or time, an external event on your PC, a counter within the virus, etc. Virus writers want their programs to spread as far as possible b

10、efore anyone notices them.</p><p>　　Many viruses go resident in the memory of your PC (like TSR). The virus may silently resident in memory waiting for you to access a diskette, copy a file, or execute a pro

11、gram, before it infects anything. Because the cause condition they use for their infection is hard to guess, viruses are more difficult to analyze.</p><p>　　Resident viruses frequently take over portions of

12、the system software on the PC to hide their existence. This technique is called stealth. Polymorphic techniques also help viruses to infect yet avoid detection.</p><p>　　Note that worms often take the opposi

13、te approach and spread as fast as possible. While this makes their detection virtually certain, it also has the effect of slowing networks and denying access.</p><p>　　Virus Behavior－Attack Phase</p>

14、<p>　　Many viruses do unpleasant things such as deleting files or changing random data on your disk, simulating typewriting or merely slowing your PC down; some viruses do less harmful things such as playing music o

15、r creating messages or animation on your screen. Just as the infection phase can be caused by some event, the attack phase also has its own cause.</p><p>　　Does this mean a virus without an attack phase is b

16、enign? No. Most viruses have bugs in them and these bugs often cause unintended negative side effects. In addition, even if the virus is perfect, it still steals system resources.</p><p>　　Viruses often dela

17、y revealing their presence by launching their attack only after they have had enough opportunity to spread. This means the attack could be delayed for days, weeks, months, or even years after the initial infection.</p

18、><p>　　The attack phase is optional, many viruses simply reproduce and have no cause for an attack phase. Does this mean that these are "good" viruses? No! Anything that writes itself to your disk wit

19、hout your permission is stealing storage and CPU cycles.</p><p>　　This is made worse since viruses that "just infect," with no attack phase, often damage the programs or disks they infect. This is

20、not an intentional act of the virus, but simply a result of the fact that many viruses contain extremely poor quality code.</p><p>　　An example, one of the most common past viruses, Stoned, is not intentiona

21、lly harmful. Unfortunately, the author did not anticipate the use of anything other than 360KB floppy disks. The original virus tried to hide its own code in an area of 1.2MB diskettes that resulted in corruption of the

22、entire diskette (this bug was fixed in later versions of the virus).</p><p>　　Number of Viruses</p><p>　　In 1990, estimates ranged from 200 to 500; then in 1991 estimates ranged from 600 to 1,00

23、0 different viruses. In late 1992, estimates were ranging from 1,000 to 2,300 viruses. In mid-1994, the numbers vary from 4,500 to over 7,500 viruses. In 1996 the number climbed over 10,000. 1998 saw 20,000 and 2000 topp

24、ed 50,000. It's easy to say there are more now.</p><p>　　The confusion exists partly because it's difficult to agree on how to count viruses. New viruses frequently arise from someone taking an exist

25、ing virus that does something like put a message out on your screen saying "Your PC is now stoned" and changing it to say something like "Donald Duck is a liar!". Is this a new virus? Most experts say

26、 yes. But, this is a trivial change that can be done in less than two minutes resulting in yet another "new" virus.</p><p>　　Another problem comes from viruses that try to conceal themselves from s

27、canners by mutating. In other words, every time the virus infects another file, it will try to use a different version of itself. These viruses are known as polymorphic viruses.</p><p>　　One example, the Wha

28、le (a huge clumsy 10,000 byte virus), creates 33 different versions of itself when it infects files. At least one person counts this as 33 different viruses on their list. Many of the large number of viruses known to exi

29、st have not been detected in the wild but probably exist only in someone's virus collection.</p><p>　　David M. Chess of IBM's High Integrity Computing Laboratory reported in the November 1991 Virus B

30、ulletin that "about 30 different viruses and variants account for nearly all of the actual infections that we see in day-to-day operation." Now, about 180 different viruses (and some of these are members of a s

31、ingle family) account for all the viruses that actually spread in the wild.</p><p>　　How can there be so few viruses active when some experts report such high numbers? This is probably because most viruses a

32、re poorly written and cannot spread at all or cannot spread without betraying their presence. Although the actual number of viruses will probably continue to be hotly debated, what is clear is that the total number of vi

33、ruses is increasing.</p><p>　　How Serious are Viruses?</p><p>　　While serious if you have one, viruses are only one way your data can be damaged. You must be prepared for all threats; many of wh

34、ich are more likely to strike than viruses.</p><p>　　It's important to keep viruses in perspective. A well-known anti-virus researcher once said that you have more to fear from a cup of coffee (which may

35、 spill) than from viruses. While the growth in number of viruses and introduction of the Microsoft Word macro viruses and Visual Basic Script worms now puts this statement into question (even though you can avoid these b

36、y just not clicking on them to open them!), it's still clear that there are many dangerous occurrences of data corruption from cau</p><p>　　So, does this mean that viruses are nothing to worry about? Emp

37、hatically, no! It just means that it's foolish to spend much money and time on addressing the threat of viruses if you've done nothing about the other more likely threats to your files. Because viruses and worms

38、are deliberately written to invade and possibly damage your PC, they are the most difficult threat to guard against. It's pretty easy to understand the threat that disk failure represents and what to do about it (alt

39、hough sur</p><p><b>　　二、英文翻譯</b></p><p><b>　　計(jì)算機(jī)病毒介紹</b></p><p>　　病毒是導(dǎo)致很多問題產(chǎn)生的一個原因，甚至有些專家也會對病毒的產(chǎn)生產(chǎn)生誤解。首先讓我們定義一下我們所說的病毒：</p><p>　　病毒就是一個能夠通過把自身附加

40、到可執(zhí)行文件之后來復(fù)制其自身代碼的程序，通過這種方式可以使得被感染的可執(zhí)行文件執(zhí)行時，病毒代碼也能夠被執(zhí)行。這里的“程序”（COM或EXE文件）指的是一個可執(zhí)行文件。附加可能指的是物理地添加到一個文件的尾部，插入到一個文件的中間，或者只是簡單地將指針放置到病毒可以在磁盤中找到的某處的不同位置。</p><p>　　許多病毒將可自復(fù)制的代碼放置到其他程序。這樣當(dāng)被感染的程序被執(zhí)行時，更多的程序就被這些可自復(fù)制的代碼

41、感染了。當(dāng)這些自復(fù)制代碼被一些事件觸發(fā)時，或許會做出一些對你的計(jì)算機(jī)有潛在危害的行為。數(shù)據(jù)文件的宏部分（如微軟的word文件）可能是更具危害性但不易被發(fā)現(xiàn)的病毒?，F(xiàn)在，為網(wǎng)站編寫的或者包括在E-mail中的腳本也能夠被執(zhí)行和感染。與病毒相似，你可以從特洛伊木馬、蠕蟲和邏輯炸彈中找到惡意代碼。</p><p>　　病毒的行為——感染階段</p><p>　　病毒有很多不同的形式，但在它們執(zhí)行

42、的過程中都有兩個階段：感染階段和攻擊階段。首先，我們先來討論感染階段。</p><p>　　病毒在執(zhí)行時，能夠感染其他程序。一些病毒會在每次被執(zhí)行時，都感染其他程序；另一些病毒只是在一些特定的觸發(fā)原因下才能感染其他程序。這個觸發(fā)原因可能是任何事件，一個日期或時間，一個計(jì)算機(jī)的外部事件，一個病毒內(nèi)部的計(jì)數(shù)器等。病毒的編寫者想讓他的程序在其他人發(fā)現(xiàn)之前盡可能地廣泛傳播。</p><p>　　許

43、多病毒像終止駐留程序那樣駐留在PC的內(nèi)存中。病毒能夠在它感染其他程序前潛伏在內(nèi)存中，等待你存取磁盤，拷貝文件或執(zhí)行一個程序。很難判斷什么是它的觸發(fā)條件，因此也很難分析它。</p><p>　　駐留內(nèi)存病毒常常代替PC系統(tǒng)文件的一部分來掩飾它的存在，這種技術(shù)叫做隱藏。多態(tài)技術(shù)也能夠幫助病毒進(jìn)行感染而不被檢測到。</p><p>　　蠕蟲病毒采用相反的方法盡可能快速地傳播。雖然能夠檢測到它的存

44、在，但它依然能使上網(wǎng)速度下降并且能拒絕訪問。</p><p>　　病毒的行為——感染階段</p><p>　　病毒有很多不同的形式，但在它們執(zhí)行的過程中都有兩個階段：感染階段和攻擊階段。首先，我們先來討論感染階段。</p><p>　　病毒在執(zhí)行時，能夠感染其他程序。一些病毒會在每次被執(zhí)行時，都感染其他程序；另一些病毒只是在一些特定的觸發(fā)原因下才能感染其他程序。這個

45、觸發(fā)原因可能是任何事件，一個日期或時間，一個計(jì)算機(jī)的外部事件，一個病毒內(nèi)部的計(jì)數(shù)器等。病毒的編寫者想讓他的程序在其他人發(fā)現(xiàn)之前盡可能地廣泛傳播。</p><p>　　許多病毒像終止駐留程序那樣駐留在PC的內(nèi)存中。病毒能夠在它感染其他程序前潛伏在內(nèi)存中，等待你存取磁盤，拷貝文件或執(zhí)行一個程序。很難判斷什么是它的觸發(fā)條件，因此也很難分析它。</p><p>　　駐留內(nèi)存病毒常常代替PC系統(tǒng)文件

46、的一部分來掩飾它的存在，這種技術(shù)叫做隱藏。多態(tài)技術(shù)也能夠幫助病毒進(jìn)行感染而不被檢測到。</p><p>　　蠕蟲病毒采用相反的方法盡可能快速地傳播。雖然能夠檢測到它的存在，但它依然能使上網(wǎng)速度下降并且能拒絕訪問。</p><p>　　病毒的行為——攻擊階段</p><p>　　許多病毒會做一些不太令人愉快的事情，比如刪除文件或者改變磁盤上的隨機(jī)數(shù)據(jù)，冒充打字稿或者只

47、是降低PC的速度；一些病毒做一些不太有害的事情，比如播放音樂或在屏幕上顯示一些信息或動畫。如同感染階段需要一些事件觸發(fā)一樣，攻擊階段也有它自己的觸發(fā)條件。</p><p>　　這是否就意味著一個沒有攻擊階段的病毒就是良性的呢？不。許多病毒其自身都有bug，這些bug會產(chǎn)生一些未知的消極影響。此外，即使病毒設(shè)計(jì)完美，它仍會盜用系統(tǒng)資源。</p><p>　　病毒可以通過當(dāng)它們擁有充足條件時才

48、開始傳播的方法來推遲暴露它們的存在。這意味著攻擊可能會被推遲到最初感染后的幾天，幾星期，幾個月甚至幾年才會發(fā)生。</p><p>　　攻擊階段是可選擇性的，許多病毒的攻擊只是簡單地進(jìn)行復(fù)制并且沒有觸發(fā)因素。是否這就可以說這些是“好”病毒呢？不！任何不經(jīng)過你允許而在你磁盤上復(fù)制自己的東西都會盜用內(nèi)存和CPU資源。</p><p>　　有些病毒只會“感染”而沒有攻擊階段，但它們會破壞被它們感染

49、的程序或磁盤，這反而更有害。這并不是這些病毒想要做的事情，而是因?yàn)樗鼈冎泻泻懿畹拇a所帶來的后果。</p><p>　　舉一個例子，一個過去最普通的病毒——Stoned——并沒有明確的破壞性。但不幸的是，病毒的編寫者并沒有預(yù)見到不同于360KB軟盤的其他磁盤的使用。最初的病毒試圖把它自身隱藏在1.2MB的磁盤中從而導(dǎo)致整張磁盤變壞（在這個病毒后來的版本中，這個bug已經(jīng)修復(fù)）。</p><p

50、><b>　　病毒的數(shù)量</b></p><p>　　在1990年，估計(jì)有200～500種病毒。到1991年，估計(jì)有600～1 000種不同的病毒。在1992年下半年，估計(jì)有1 000～2 300種病毒。1994年中期有4 500～7 500種病毒。1996年就超過了10 000種。1998年大概是20 000種，到2000年就達(dá)到50 000種。很明顯，現(xiàn)在病毒越來越多了。</

51、p><p>　　由于在怎樣計(jì)算病毒上很難達(dá)成一致，所以現(xiàn)在還存在一些混亂。新病毒往往是由已經(jīng)存在的病毒經(jīng)過一些變化產(chǎn)生的。例如，把輸出到屏幕上的信息由“你的PC現(xiàn)在被石化了”改為“Donald Duck是個騙子！”這是一種新的病毒么？大部分病毒專家會說是。但是，一個在兩分鐘內(nèi)可以完成的細(xì)微的改動就產(chǎn)生了一種“新”病毒。</p><p>　　另一個問題是由于一些病毒是通過變異的方式試圖使它不被病

52、毒掃描器發(fā)現(xiàn)而產(chǎn)生的。換句話說，每次這個病毒感染了另一個文件，就會產(chǎn)生一個不同的版本。這些病毒被認(rèn)為是多態(tài)性病毒。</p><p>　　舉一個例子，病毒W(wǎng)hale（一個巨大笨拙的10 000字節(jié)的病毒），當(dāng)它感染文件時能夠產(chǎn)生33種不同的版本。有人就將這作為33種不同的病毒列在他的病毒列表里了。很多病毒雖然還沒有被公眾檢測到，但可能已經(jīng)在某個人的病毒收集夾中了。</p><p>　　IBM

53、高集成計(jì)算機(jī)實(shí)驗(yàn)室的David M. Chess在1991年11月發(fā)表的病毒公告上說：“大概30種不同的病毒及其變種就能夠說明幾乎所有我們所見的實(shí)際的病毒感染。”現(xiàn)在，大概180種病毒（這些當(dāng)中的一部分屬于一個病毒家族）就可以概括所有現(xiàn)在實(shí)際傳播中的病毒。</p><p>　　為什么有些專家報(bào)道如此巨大的數(shù)字而只有這么少的病毒在活動呢？很可能是因?yàn)榇蟛糠植《揪帉懖顒?，?dǎo)致其根本不能傳播，或者在不暴露自己存在的情況

54、下不能傳播。雖然關(guān)于病毒的實(shí)際數(shù)量可能會繼續(xù)進(jìn)行激烈的爭論，但一個很清楚的事實(shí)就是病毒的總數(shù)在增加。</p><p><b>　　病毒真的很可怕么？</b></p><p>　　雖然如果你的機(jī)器被病毒感染會許多威協(xié)帶來很嚴(yán)重的后果，但那只是你的數(shù)據(jù)被破壞的其中一種方式。你必須準(zhǔn)備應(yīng)對所有的威脅，許多威協(xié)比病毒的威力還要大。</p><p>　　

55、正確對待病毒是很重要的。一位著名的反病毒專家說過，“也許一杯咖啡（可能會灑）會帶來比病毒更大的威脅。”雖然病毒的數(shù)量在增加，并且現(xiàn)在微軟Word宏病毒和Visual Basic腳本蠕蟲的出現(xiàn)對這一說法產(chǎn)生了質(zhì)疑（即使你可以不去點(diǎn)擊它們來避免感染?。苊黠@，仍有很多其他的原因?qū)е聰?shù)據(jù)崩潰。</p><p>　　那么，是否說病毒并不值得憂慮??？大聲地說，不！只是說，如果沒有防范其他會對你文件造成的威脅，而花費(fèi)過多