The only way to ensure that deleted files, as well as files that youencrypt with EFS, are safe from recovery is to use a secure deleteapplication. Secure delete applications overwrite a deleted file'son-disk data using techniques that are shown to make disk dataunrecoverable, even using recovery technology that can read patterns inmagnetic media that reveal weakly deleted files. SDelete (SecureDelete) is such an application. You can use SDelete both to securelydelete existing files, as well as to securely erase any file data thatexists in the unallocated portions of a disk (including files that youhave already deleted or encrypted). SDelete implements the Departmentof Defense clearing and sanitizing standard DOD 5220.22-M, to give youconfidence that once deleted with SDelete, your file data is goneforever. Note that SDelete securely deletes file data, but not filenames located in free disk space.
SDelete is a command line utility that takes a number of options. Inany given use, it allows you to delete one or more files and/ordirectories, or to cleanse the free space on a logical disk. SDeleteaccepts wild card characters as part of the directory or file specifier.
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Securely deleting a file that has no special attributes is relativelystraight-forward: the secure delete program simply overwrites the filewith the secure delete pattern. What is more tricky is securely deletingWindows NT/2K compressed, encrypted and sparse files, and securelycleansing disk free spaces.
Compressed, encrypted and sparse are managed by NTFS in 16-clusterblocks. If a program writes to an existing portion of such a file NTFSallocates new space on the disk to store the new data and after the newdata has been written, deallocates the clusters previously occupied bythe file. NTFS takes this conservative approach for reasons related todata integrity, and in the case of compressed and sparse files, in casea new allocation is larger than what exists (the new compressed data isbigger than the old compressed data). Thus, overwriting such a file willnot succeed in deleting the file's contents from the disk.
Cleaning free space presents another challenge. Since FAT and NTFSprovide no means for an application to directly address free space,SDelete has one of two options. The first is that it can, like it doesfor compressed, sparse and encrypted files, open the disk for raw accessand overwrite the free space. This approach suffers from a big problem:even if SDelete were coded to be fully capable of calculating the freespace portions of NTFS and FAT drives (something that's not trivial), itwould run the risk of collision with active file operations taking placeon the system. For example, say SDelete determines that a cluster isfree, and just at that moment the file system driver (FAT, NTFS) decidesto allocate the cluster for a file that another application ismodifying. The file system driver writes the new data to the cluster,and then SDelete comes along and overwrites the freshly written data:the file's new data is gone. The problem is even worse if the cluster isallocated for file system metadata since SDelete will corrupt the filesystem's on-disk structures.
The second approach, and the one SDelete takes, is to indirectlyoverwrite free space. First, SDelete allocates the largest file itcan. SDelete does this using non-cached file I/O so that the contentsof the NT file system cache will not be thrown out and replaced withuseless data associated with SDelete's space-hogging file. Becausenon-cached file I/O must be sector (512-byte) aligned, there might besome leftover space that isn't allocated for the SDelete file evenwhen SDelete cannot further grow the file. To grab any remaining spaceSDelete next allocates the largest cached file it can. For both ofthese files SDelete performs a secure overwrite, ensuring that all thedisk space that was previously free becomes securely cleansed.
On NTFS drives SDelete's job isn't necessarily through after itallocates and overwrites the two files. SDelete must also fill anyexisting free portions of the NTFS MFT (Master File Table) with filesthat fit within an MFT record. An MFT record is typically 1KB in size,and every file or directory on a disk requires at least one MFT record.Small files are stored entirely within their MFT record, while filesthat don't fit within a record are allocated clusters outside the MFT.All SDelete has to do to take care of the free MFT space is allocatethe largest file it can - when the file occupies all the available spacein an MFT Record NTFS will prevent the file from getting larger, sincethere are no free clusters left on the disk (they are being held by thetwo files SDelete previously allocated). SDelete then repeats theprocess. When SDelete can no longer even create a new file, it knowsthat all the previously free records in the MFT have been completelyfilled with securely overwritten files.
The reason that SDelete does not securely delete file names whencleaning disk free space is that deleting them would require directmanipulation of directory structures. Directory structures can have freespace containing deleted file names, but the free directory space is notavailable for allocation to other files. Hence, SDelete has no way ofallocating this free space so that it can securely overwrite it.
The Centers for Medicare & Medicaid Services (CMS) is pleased to make the Medicare Current Beneficiary Survey (MCBS) Public Use File (PUF) available to the public as a free download. This PUF is intended to support studies requiring the use and analysis of Medicare data.
The Amazon S3 File Gateway enables you to store and retrieve objects in Amazon Simple Storage Service (S3) using file protocols such as Network File System (NFS) and Server Message Block (SMB). Objects written through S3 File Gateway can be directly accessed in S3.
The Amazon FSx File Gateway enables you to store and retrieve files in Amazon FSx for Windows File Server using the SMB protocol. Files written through Amazon FSx File Gateway are directly accessible in Amazon FSx for Windows File Server.
You use the AWS Management Console to download the virtual appliance gateway or purchase the hardware appliance, configure storage, and manage and monitor the service. The gateway connects your applications to AWS storage by providing standard storage interfaces. It provides transparent caching, efficient data transfer, and integration with AWS monitoring and security services.
An object that needs to be accessed by using a file share should only be managed by the gateway. If you directly overwrite or update an object previously written by Amazon S3 File Gateway, it results in undefined behavior when the object is accessed through the file share.
To reduce latency and number of Amazon S3 requests, Amazon S3 File Gateway only scans the headers for file metadata associated with the objects when you explicitly list the files or directories. File metadata is collected as a part of that scan; file contents are downloaded only when the object is read.
The gateway does not automatically download full objects or all the data that exists in your bucket; data is only downloaded when it is explicitly accessed by your clients. Additionally, to reduce data transfer overhead, File Gateway uses multipart uploads and copy put, so only changed data in your files is uploaded to S3.
No. We recommend a single writer to objects in your S3 bucket. If you directly overwrite or update an object previously written by File Gateway, it results in undefined behavior when the object is accessed through the file share. Concurrent modification of the same object (e.g. via the S3 API and the Amazon S3 File Gateway) can lead to unpredictable results and we recommend against this configuration.
If using S3 event notifications you may receive events for partial files created by the gateway to ensure your data is durably stored in S3. Partial files may occur for a number of reasons, such as the gateway needing to free up cache space, or a high rate of writes to a file. These partial files may not be application consistent.
The local cache should generally be sized for the working set of data that you need low-latency access to. If the cache is too small then read latencies will increase as data being requested must be fetched from S3, and writes could fail if there is no free cache space to store data locally pending upload to S3.
You should provision your cache based on: 1/ The size of your working dataset to which you need low-latency access, so you can reduce read latencies by decreasing the frequency with which data is requested from S3, and 2/ The size of files written to the gateway by your applications.
Smaller cache disks can result in poor performance and failures during writes if there is no free cache space to store data locally when pending upload to S3. To learn more about monitoring your cache usage, refer to Monitoring Your File Share in the documentation.
Amazon S3 File Gateway uses multipart uploads and copy put, so only changed data is uploaded to S3, which can reduce data transfer. The gateway does not automatically download full objects or all the data that exists in your bucket; data is only downloaded when explicitly accessed by your NFS client.
To use Amazon FSx File Gateway, you need to have at least one running Amazon FSx file system, and ensure that you have on-premises access to Amazon FSx for Windows File Server either through a VPN or through an AWS Direct Connect connection. To get started with FSx for Windows File Server, view the documentation instructions here. You then begin either by downloading and deploying an Amazon FSx File Gateway VMware virtual appliance, or an AWS Storage Gateway hardware appliance into your on-premises environment. Once your Amazon FSx File Gateway is installed and you can access FSx for Windows File Server, you can use the AWS Management Console to attach an FSx for Windows File Server file system. The AWS Management Console will then walk you through all the steps needed to make file shares accessible on premises. 2ff7e9595c
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