![]() The problem is even worse if the cluster isĪllocated for file system metadata since SDelete will corrupt the file The file system driver writes the new data to the cluster,Īnd then SDelete comes along and overwrites the freshly written data: To allocate the cluster for a file that another application is For example, say SDelete determines that a cluster isįree, and just at that moment the file system driver (FAT, NTFS) decides Would run the risk of collision with active file operations taking place Space portions of NTFS and FAT drives (something that's not trivial), it This approach suffers from a big problem:Įven if SDelete were coded to be fully capable of calculating the free The first is that it can, like it doesįor compressed, sparse and encrypted files, open the disk for raw accessĪnd overwrite the free space. Provide no means for an application to directly address free space, The file's data, it can open the disk for raw access and overwrite thoseĬleaning free space presents another challenge. Once SDelete knows which clusters contain Which clusters on a disk are occupied by data belonging to compressed, Using the defragmentation API, SDelete can determine precisely To handle these types of files SDelete relies on the defragmentationĪPI. Not succeed in deleting the file's contents from the disk. NTFS takes this conservative approach for reasons related toĭata integrity, and in the case of compressed and sparse files, in caseĪ new allocation is larger than what exists (the new compressed data isīigger than the old compressed data). If a program writes to an existing portion of such a file NTFSĪllocates new space on the disk to store the new data and after the newĭata has been written, deallocates the clusters previously occupied by Windows NT/2K compressed, encrypted and sparse files, and securelyĬompressed, encrypted and sparse are managed by NTFS in 16-clusterīlocks. Straight-forward: the secure delete program simply overwrites the file Securely deleting a file that has no special attributes is relatively ![]()
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