What is a Zip File?


What are “zip” files and are they safe to open as e-mail attachments?

- Janice


This question was answered on September 16, 2005. Much of the information contained herein may have changed since posting.

The zip file extension generally denotes a compressed file format that is also referred to as an archive file.

The purpose of the zip format is to reduce data to a much smaller size for storage (archiving) or to reduce download speeds on the Internet and in e-mail.

If, for instance, you wanted to send 5 photographs via e-mail to a friend, you could reduce the amount of time that it takes your system to send the message and more importantly save the recipient time during the download if you were to zip them into 1 smaller file.

Depending upon the original file type (pictures, documents, music, etc.) you can achieve up to an 80% svings in space by zipping Some folks use it to free up hard drive space by taking older data that is not needed on a regular basis and archiving it as a single zip file.

Users of Windows XP have support built into the operating system (right-click on any file) for creating and opening zip files; look for the Compressed (zipped) Folder option.

If you highlight a series of files in any Windows XP file interface, you can right-click and choose the compression option to compress them all into a single file.

If you have an older version of Windows, you will need to install a utility that gives you the ability to create and open zip files

The most popular commercial products include WinZip, StuffIt and PKZip and free programs include 7-Zip and FilZip.

From a safety standpoint, zip files are probably amongst the most dangerous because they can contain just about anything inside of them Unless you are absolutely certain that a known sender is sending you information that has been zipped, do not ever open them.

Malicious programmers are using blended threats to attacking your system and the use of zip files play a role in many of their attempts Blended threats merge the characteristics of viruses, worms, Trojan Horses, and other malicious code with operating system and Internet vulnerabilities in a single attack By using multiple methods and techniques, hackers are counting on one of the areas of vulnerability to be open on your system so they can gain access.

There is a current outbreak of a variant of the Beagle worm that is using zip files to infect users The characteristics can vary, but the infected messages generally have blank Subject lines and have one the following zip files as an attachment:









Even if your system is completely up-to-date with all of the security patches and anti-virus updates, opening a rogue attachment file can sometimes disable all of your security systems and leave you completely vulnerable, so dont let your curiosity get the best of you and your computer!

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Posted by Ken of Data Doctors on September 16, 2005