ESET LAN Update Server 2.7, Installation Manual

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Administration Installation Guide
5
HTTP: Active & Passive modes
The download popup window is shown only for applications set to Active
mode (Higher efficiency) in the HTTP scanner compatibility (default).
With IMON in Passive mode , portions of a downloaded file are
continuously passed on to the target application whilst IMON stores a
temporary copy of each of the fragments. When the last fragment is
detected, the whole file is scanned for viruses. If an infiltration is detected,
a warning window appears and the connection with the particular server
is terminated. A disadvantage of that is that the already downloaded
portion of the file may already contain a fundamental portion of a malicious
code. What’s more, if the application repeatedly attempts to download an
infected file, it may use the already downloaded data and request only the
rest of the file. In this case, IMON may not find anything suspicious in the
remaining portion.
In Active mode (default), IMON first downloads and scans the whole file
and then passes it on to the target application. This procedure is safer
because in the case of an infiltration, the application does not receive
any portion of the downloaded file. A disadvantage is that the application
receives all the data at once, therefore it cannot show the download status
properly. Therefore, if the download lasts for more than 55 seconds (default,
but can be altered), a small window showing the download progress pops
up. Active mode is not suitable for certain types of data which requires a
continual data flow (e.g. multimedia, streaming video/audio).