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OS File Checksum Test
A checksum is a simple type of redundancy check that is used to detect errors in files.
Errors may frequently occur in files when the files are written to a disk, transmitted across a network or otherwise manipulated. The errors can even be very small - for example, a single incorrect bit - but even such small errors can greatly affect the quality of data and make it useless. For example, you can apply a checksum to an installation file after it is received from the download server to check for errors after the download, as such errors can render the corresponding software uninstallable.
To alert administrators to such integrity issues with system files that they deem critical, eG periodically runs the OS File Checksum test. This test creates a checksum by calculating the binary values (using a pre-defined algorithm) of every file configured for monitoring and storing the results. Each time the test runs, a new checksum is calculated and compared with the existing checksum. If there is a non-match, the test promptly alerts administrators to it, as it could be because of errors in the file.
Target of the test : Any Unix/Windows host system
Agent deploying the test : An internal agent
Outputs of the test : One set of results for each configured directory path
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Measurement | Description | Measurement Unit | Interpretation | ||||||
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Has checksum been modified: |
Indicates whether/not the checksum value of this file has changed since the last measurement period. |
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If the checksum value of a file has changed since the last time this test ran, then the value of this measure will be Yes. In this case, you can use the detailed diagnosis of this test to know what was the previous checksum value and the new checksum value of each test. Typically, a change in the checksum value indicates an error. If there is no change in the checksum value, then this measure will report the value No. Note that the value No does not imply that there is no error. It simply means that the test could not detect any errors. Among the types of errors that cannot be detected by simple checksum algorithms are reordering of the bytes, inserting or deleting zero-valued bytes and multiple errors that cancel each other out The numeric values that correspond to the measure values discussed above are as follows:
Note: By default, the test reports the Measure Values listed in the table above to indicate whether/not the checksum value has changed. In the graph of this measure however, the same is represented using the numeric equivalents only. |