ICAP Preview mode allows to specify files which do not require scanning (e.g., streaming video and audio) and, therefore, Dr.Web ICAPD does not need to download them. This feature allows to decrease the amount of both external traffic (by filtering access by MIME type, size or host name) and internal traffic (using Allow 204 and preview_size = 0 modes). As a result, ICAP preview mode helps improve overall speed and enhance comfort of user operation.
Rules to define files which do not require scanning (depending on the content type and size) are specified in the configuration file. For details, refer to Setting Content Filtering by MIME Type and Size.
When using Squid version 2.*, it is highly recommended to disable ICAP preview mode both in drweb-icapd (UsePreview = No) and Squid (icap_preview_enable off and icap_preview_size -1).
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Note that specifying any value other than 0 for the icap_preview_size parameter when ICAP preview is enabled, as well as specifying any value other than -1 when ICAP preview is disabled has no effect (that is, size of previewed objects currently cannot be adjusted). |
Currently, instead of ICAP preview mode, SafeSquid proxy server allows to view total amount of downloaded data.