An archive file is a collection of data files that have been packaged together. This is done to save space (when backing up a series of files to removable media, for example) or to save data transmission time (when making files available for download or when transferring them via e-mail, for example).

Programs that compress data into archive files are called archivers. WinZip is probably the best known of these: in fact, many people equate ‘zipping’ a file with archiving it, even when using a different archiver.

There are numerous archiving programs on the market, though the most familiar include WinZip and WinRAR. Most are capable of creating and accessing ZIP files, in addition to whatever format the program is designed to product. The most common archive file formats are ZIP, RAR, ARJ and CAB. The CAB format is used to archive many Microsoft® Windows® distribution files.

It’s important for anti-virus programs to scan inside these files. Otherwise any archived file could provide a convenient hiding place for malicious code. Some e-mail worms have even been deliberately distributed as archive attachments.

Good anti-virus programs also scan recursively (a ZIP within a ZIP, for example) and include a smart algorithm to avoid extracting archive bombs.