Quote:
Originally Posted by haertig
RAR takes all the files it is given and compresses them into one blob. This enables it to find similarities that occur in different files and use that to achieve far better overall compression given files that contain similar stuff (human readable documents for example). This also means that you cannot extract a single file from a RAR archive. You have to extract them all, then ignore the ones you don't want.
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Solid archive, 7z does it too, though I think the solid block option is halfway between completely solid and each file individually compressed. Higher compression, combined with the recovery record (7z doesn't have) and ability to store NTFS attributes, is why I prefer to use RAR for archiving/backup purposes.
Quote:
Originally Posted by haertig
As a side effect, this might make RAR's better for spreading malware, since you can't pick and choose what specific contents you want to decompress.
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Additionally: NTFS alternate data streams. You can use them to hide a file inside a different file. Usually they're discarded when a file moves between computers, but RAR can preserve them, which means that you can sneak malware in there. I think at least a few antiviruses make a point of checking them now.