B

　　A computer virus is a program or piece of code that is loaded onto your computer without your knowledge and runs against your wishes. All computer viruses are man－made. Here are some virus prevention tips.

　　Do not open any files attached to an email from an unknown, suspicious or untrustworthy source.

　　Do not open any files attached to an email unless you know what it is, even if it appears to come from a dear friend or someone you know. Some viruses can replicate(复制) themselves and spread through email. Better be safe than sorry and confirm that they really sent it .

　　Do not open any files attached to an email if the subject line is questionable or unexpected. If the need to do so is there, always save the file to your hard drive before doing so.

　　Delete chain emails and junk emails. Do not forward(转寄) or reply to any of them. These types of email are considered spam(垃圾邮件), which contains lots of annoying advertisements and useless information.

　　Do not download any files from strangers.

　　Be careful when downloading files from the Internet. Ensure that the source is a legitimate(合法的) and reputable one. Verify(证实) that an antivirus program checks the files on the download site. If you are uncertain, don‘t download the file at all or download the file to a floppy(软盘) and test it with your own antivirus software.

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