What are computer viruses?
According to Fred Cohen’s well-known definition, a computer virus is a computer program that can infect other computer programs by modifying them in such a way as to include a copy of itself.
Computer viruses are bits of code that damage or erase information, files, or software programs in your computer, much like viruses that infect humans, computer viruses can spread, and your computer can catch a virus when you download an infected file from the Internet or copy an infected file from a diskette. Once the viruses is embedded into your computer’s files, it can immediately start to damage or destroy information, or it can wait for a particular date or event to trigger its activity.
What are the main types of viruses?
Generally, there are two main classes of viruses. The first class consists of the file Infectors which attach themselves to ordinary program files. These usually infect arbitrary .COM and/or .EXE programs, though some can infect any program for which execution is requested, such as .SYS,.OVL,.PRG,&.MNU files.
The second class is system or boot-record infectors: those viruses, which infect executable code, found in certain system areas on a disk that are not ordinary f

什么是計算機病毒？
按照 Fred Cohen 的廣為流傳的定義，計算機病毒是一種侵入其他計算機程 序中的計算機程序，他通過修改其他的程序從而將自身的復(fù)制品嵌入其中。
計算機病毒是一些能破壞或刪除計算機中的信息、文件或程序的代碼。正如 感染人體的病毒一樣，計算機病毒能夠擴散。當(dāng)你的計算機從互聯(lián)網(wǎng)上下載一個 被感染的文件，或者從磁盤上復(fù)制一個被感染的文件時，你的計算機就會染上病 毒。而一旦病毒進入到你的計算機文件中，它就能馬上破壞或摧毀其中的信息， 或者等到某個特殊的日期或事件來臨時才觸發(fā)其破壞活動。
個人計算機病毒主要有哪些類型？
一般來說，主要存在著兩類計算機病毒。第一類由文件感染型病毒組成，他 們將自身依附在普通的程序文件上。這些病毒通常感染任意的.COM 和/或 EXE 文件，盡管有些也感染具有執(zhí)行功能的文件，如.SYS，.OVL，.PRG 和.MNU 文件.
第二類病毒是系統(tǒng)病毒或引導(dǎo)區(qū)記錄感染型病毒，這些感染可執(zhí)行代碼的病 毒出現(xiàn)在磁盤的某些系統(tǒng)區(qū)中，而不是普通文件中。在 DOS 系統(tǒng)中，常見的引導(dǎo) 扇區(qū)病毒和主引導(dǎo)記錄病毒，前者只感染 DOS 引導(dǎo)扇區(qū)，后者感染硬盤的主引導(dǎo) 記錄和軟盤的 DOS 引導(dǎo)扇區(qū)。第二類病毒的例子包括大腦病毒、大麻病毒、帝國 病毒、Azusa 以及米開郎基羅病毒等，此類病毒通常為駐留型病毒。
哪些文件可以傳播計算機病毒？