He measured data remanence after repeated wipes, and saw that after 31 passes, he was unable (with expensive equipment) to distinguish a multiply-overwritten one from a multiply-overwritten zero. The article that started it is “Secure Deletion of Data from Magnetic and Solid-State Memory” by Peter Gutmann, presented at USENIX in 1996. “The urban legend of multipass hard disk overwrite and DoD 5220-22-M” by Brian Smithson has a good overview of the topic. However, Gutmann's work has been somewhat overhyped, and does not extend to modern disks. The origin lies in work by Peter Gutmann, who showed that there is some memory in a disk bit: a zero that's been overwritten with a zero can be distinguished from a one that's been overwritten with a zero, with a probability higher than 1/2. Multiple passes erase a tree with overkill but miss the rest of the forest. '.Summary: it was marginally better on older drives, but doesn't matter now. The code I am using is this: if (!file_exists('/path/to/Files/'. If I manually delete the 0 byte file and have the member go back to the page, about 50-60% of the time, the file is created successfully, the rest of the time, another 0-byte file. Meanwhile, those same browsers, OSes and country locations also have successful file creations. It happens to all OSes, on all browsers and so far in at least 17 different countries. I have checked everything I can think of. The member after them, perfect execution. However, recently I have had about 30% of new members creating their accounts, logging in and visiting the page and their created file is 0 bytes. The file creation works well and it does exactly what it is supposed to. The file is named "memberUserName.php" and stored outside of root.
I have a page for members that when accessed for the very first time, a file of variables is created for them. I am having some strange behavior and I cannot find a reason for it.
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