virus英语作文

在近几年高考中,大多数考生的英语写作水平旗鼓相当,如何能在考试中写出一篇高水平的英语作文呢?下面小编分享 virus英语作文给你们，希望对你们有用。?　　virus英语作文如下：?　　A computer virus is a computer program that can copy itself and infect a computer without permission or knowledge of the user. The original may modify the copies or the copies may modify themselves, as occurs in a metamorphic virus. A virus can only spread from one computer to another when its host is taken to the uninfected computer, for instance by a user sending it over a network or carrying it on a removable medium such as a floppy disk, CD, or USB drive. Additionally, viruses can spread to other computers by infecting files on a network file system or a file system that is accessed by another computer. Viruses are sometimes confused with computer worms and Trojan horses. A worm, however, can spread itself to other computers without needing to be transferred as part of a host. A Trojan horse is a file that appears harmless until executed. In contrast to viruses, Trojan horses do not insert their code into other computer files. Many personal computers are now connected to the Internet and to local-area networks, facilitating their spread. Today's viruses may also take advantage of network services such as the World Wide Web, e-mail, and file sharing systems to spread, blurring the line between viruses and worms. Furthermore, some sources use an alternative terminology in which a virus is any form of self-replicating malware.?　　The term comes from the term virus in biology. A computer virus reproduces by making (possibly modified) copies of itself in the computer's memory, storage, or over a network. This is similar to the way a biological virus works.?　　Some viruses are programmed to damage the computer by damaging programs, deleting files, or reformatting the hard disk. Others are not designed to do any damage, but simply replicate themselves and perhaps make their presence known by presenting text, video, or audio messages. Even these benign viruses can create problems for the computer user. They typically take up computer memory used by legitimate programs. As a result, they often cause erratic behavior and can result in system crashes. In addition, many viruses are bug-ridden, and these bugs may lead to system crashes and data loss.?　　There are many viruses operating in the general Internet today, and new ones are discovered every day.?　　The computer virus is an outcome of the computer overgrowth in the 1980s．The cause of the term "computer virus" is the likeness between the biological virus and the evil program infected with computers．The origin of this term came from an American science fiction“ The Adolescence of P－1“　written by Thomas J. Ryan，published in 1977．Human viruses invade a living cell and turn it into a factory for manufacturing viruses. However, computer virusesare small programs. They replicate by attaching a copy of themselves to another program.?　　Once attached to me host Program，the viruses then look for other programs to "infect"．In this way， he virus can spread quickly throughout a hard disk or an entire organization when it infects a LAN or a multi-user system． At some point，determined by how the virus was programmed the virus attacks．The timing of the attack can be linked to a number of situations，including a certain time or date， the presence of a particular file，the security privilege level of the user，and the number of times a file is used．Likewise，the mode of attack varies．So－called "benign" viruses might simply display a message，like the one that infected IBM’s main computer system last Christmas with a season’s greeting．Malignant viruses are designed to damage the system．The attack is to wipe out data， to delete flies， or to format the hard disk.?　　What Kind of Viruses Are There？ There are four main types of viruses: shell, intrusive, operating system and source ode． Shell viruses wrap themselves around a host program and don’t modify the original program．Shell programs are easy to write，which is why about half of viruses are of this type． 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.