翻译；What Kind OF viruses Are There?


1995-11-24

        There are four main types of viruses:shell,intrusive,operating system,and source code.
        Shell viruses wrap themselves around a host program and do not modify the original program.Shell programs are easy to write,which is why about half of-all viruses are of this type.In addition ,shell viruses are easy for programs like Data Physician to remove.
        Intrusive viruses invade an existing program and actually insert a portion of themselves into the host program.Intrusive viruses are hard to write and very difficult to remove without damaging the host file.
        Shell and intrusive viruses most commonly attack executable program files-those with a.COM or .EXE extension--although data files are also at some risk.
        Operating system virses work by replacing parts of the opersting system with their own logic.Very difficult to write,these viruses have the ability,once booted up,to take total control of your system.
        Source code viruses are intrusive programs that are inserted into a source program such as those written in Pascal prior to thd program being compiled.there are the last-common viruses be cause they are not only hard to write,but also have a limited number of hosts compared to the other types.
        病毒程序有哪几种
        有四种类型的病毒程序：外壳型，入侵型，操作系统型的和源码型。
        外壳型病毒将它们自己包裹在主程序的四周，对源程序不作修改。外壳型病毒容易编写，此约半数病毒程序是这种类型。此外，外壳型病毒容易被Date Physiciam(数据医生)之类程序去除掉。
        入侵型病毒侵入到现有程序中，实际上把病毒程序的一部分插入主程序。入侵型病毒难以编写，破坏主文件就难以去除。
        外壳型和入侵型病毒通常都是攻击可执行程序文件----带有.COM或者.EXE扩展名---虽然数据文件有受攻击的危险。
        操作系统型病毒工作时用它们自己的逻辑代替部分操作系统。这些病毒程序的编写非常困难，它们一旦得手就有能力控制整个系统。
        源码型病毒是入侵程序，它们在程序被编译之前插入到诸如用PASCAL编写的源程序中，它们是最少见的病毒程序，因为它们不仅编写困难，而且与其它类型的病毒相比，受它们破坏的主程序数目也有限。
 
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