F-SECURE ANTI-VIRUS FOR MICROSOFT EXCHANGE 7.10 Administrator's Manual page 115

Choose advanced processing options for all the messages processed
during the scheduled operation.
Processing options
Incremental scanning Specify whether you want to process all
Advanced options
Intelligent file type
recognition
Limit max levels of
nested messages
Centrally Managed Administration
messages or only those messages that have not
been processed previously during the scheduled
processing.
Select whether you want to use Intelligent File
Type Recognition or not.
Trojans and other malicious code can disguise
themselves with filename extensions which are
usually considered safe to use. Intelligent File
Type Recognition can recognize the real file type
of the message attachment and use that while
the attachment is processed.
Using Intelligent File Type Recognition
strengthens the security but can degrade the
system performance.
Specify how many levels deep to scan in nested
e-mail messages. A nested e-mail message is a
message that includes one or more e-mail
messages as attachments. If zero (0) is
specified, the maximum nesting level is not
limited.
It is not recommended to set the maximum
nesting level to unlimited as this will make the
product more vulnerable to DoS
(Denial-of-Service) attacks.
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