So I heard this guy talkin about how one time he deleted someone's windows directory remotely. He claimed to have gotten into the system and deleted it such that the files are all still there, but the OS can't find them. I might be coming up with the wrong name.... But about my specific question: how did he do this and how can I protect myself from it? I'm guessing he SSH'ed into the guy's system and just did it from the command line. I'm looking for more info on this potential security hazard. Thanks.
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I don't know what OS it is he used, it sound more like windows as NTFS filesystem supports alternate data streams which could be used to make the file look empty even though it contains data.
Also a delete on most filesystems only deletes an index entry or marks it as deleted for overwrite in the future, could this be what he was incorrectly referring to?