E-mail attachments are files that are sent to another user's e-mail box that are in formats most e-mail-reading programs do not recognise. These files can be downloaded to your computer. They are a convenient way to share files, but e-mail attachments carry certain risks, even when they come from known sources.
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Viruses and Trojans
Viruses and Trojans are often sent through e-mail attachments. While phishing scams are a danger of e-mail, these do not require a file to be transferred to your computer. Viruses can come in the forms of word macros, visual basic script files and executable files. Viruses are bits of malicious code that can replicate themselves. They usually infect other programs. A Trojan is a program that masquerades as another program when it is downloaded. Many spyware programs fall into this category. Viruses can slow down your computer, erase files or, in the case of the recent Conficker virus, infect your computer with a virus that tells you your system was infected, slows down system functions and wants you to download software from that company. When you get too many pop-ups in Internet Explorer, a Trojan is usually the cause. Mozilla Firefox users notice this less because Mozilla browsers perform better at blocking unwanted pop-ups, but they do not prevent spyware, virus or Trojan infections.
Masked File Extensions
Many files will be named in this format: "filename.txt.vbs" or "filename.zip.exe." The ".txt" and ".zip" files are usually benign extensions--the second extension shows the file's true nature. Both files are executable Microsoft Windows files. Windows users can direct the operating system to show extensions. This lets you know the difference between a standard file that usually poses no risk and files that can potentially harm your system. The danger posed by masked file extensions is that you will think you are opening a benign document when it could be a harmful excecutable code. This can be prevented by reading the names of e-mail attachments thoroughly.
".shs" File Extension
Another type of executable file, with the extension ".shs," affects only Windows users, but it deserves special attention because Windows does not show this file extension, even if you adjust your display settings for files. The only way to force Windows to show ".shs" files is to edit the system's registry. Because changing the values in this system file can have undesirable effects, even for experienced users, you should edit the system registry only as a last resort.
Dangers of Microsoft Word Documents
Microsoft Word documents sometimes contain macros that contain viruses. Word documents are inefficient ways to send short messages. Instead of sending Word documents and all of its inherent dangers, use plain text. It must be edited in a word processor, and you should consider saving the document in rich text format. All modern word processors can read rich text files. The formatting for the malicious code will not be executed when the document is opened. The Word Marker virus, often sent in Word documents, checks for stored passwords in your browser directory and sends these to hack sites.
Anti-Virus Programs Can Help
Norton AntiVirus, Avast Antivirus and many other antivirus programs are capable of scanning e-mail attachments before you download them. Some web mail programs, such as Yahoo!'s e-mail service, scan attachments before you download them. If you must open an e-mail attachment, make sure the file comes from a source you trust, and scan each attachment before opening it on your computer.
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