As every moderately adept computer user knows, you can add attachments to emails. You can attach documents, photos, or perhaps music to your emails and send them to any recipient you desire. The unfortunate fact is that some computer users have decided to design attachments that can cause a great deal of harm to your computer. An email attachment could potentially cause your computer to run slow, send your passwords to unknown recipients over the internet, and corrupt or destroy completely your personal files or your hard drive.
The point is not to avoid opening any email attachments at all, but to be aware of harmful file extensions, avoid opening attachments from people you do not know, and make sure you have a good anti-virus program installed on your computer. The are some types of viruses and Trojan Horses that will cause your email software, such as Outlook, to resend email messages containing harmful attachments with your name as the sender, without your knowledge. Some of these harmful attachments operate so quickly that your entire computer could be infected before your anti-virus software has time to alert you to their presence. Email attachments with file extensions such as .jpg, .bmp, and .txt are generally safe to open.
If an email attachment you receive contains file extensions such as url, .doc, or .xls, you can generally consider them safe if you know the sender, but these extensions are capable of causing damage to your computer, so be very careful if you are uncertain or unfamiliar with the sender. Files containing the extensions .exe, .vbs, and .com should be treated with extreme caution. Executable files, Visual Basic Script, and .com extensions have the power to do a lot of harm to your computer, and possibly your entire network if you are in an office environment.
These are just a sample of the possible file extensions and the damage they may or may not cause, but you need to be certain your anti-virus software is up to date and that you use extreme caution in opening email attachments. Opening a single email attachment from an unknown source could infect your entire computer.