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A second issue is that the extraction process can cause excessive consumption of system resources. This may result in a denial-of-service attack when resource usage is disproportionately large in comparison to the input data. The zip algorithm can produce very large compression ratios [Mahmoud 2002]. For example, a file consisting of alternating lines of a characters and b characters can achieve a compression ratio of more than 200 to 1. Even higher compression ratios can be obtained using input data that is targeted to the compression algorithm. This permits the existence of zip bombs in which a small ZIP or GZIP file consumes excessive resources when uncompressed. An example of a zip bomb is the file 42.zip which is a zip file consisting of 42 kilobytes of compressed data, containing five layers of nested zip files in sets of 16, each bottom layer archive containing a 4.3 gigabyte (4 294 967 295 bytes; ~ 3.99 GiB) file for a total of 4.5 petabytes (4 503 599 626 321 920 bytes; ~ 3.99 PiB) of uncompressed data. Zip bombs often rely on repetition of identical files to achieve their extreme compression ratios. Programs must either limit the traversal of such files or refuse to extract data beyond a certain limit. The actual limit depends on the capabilities of the platform and expected usage.
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FIO99-J. Use conservative file naming conventions Rule 00: Input Validation and Data Sanitization (IDS)