These scenarios are discussed in more detail
in Chapter 7.
ISA performs this type of OWA securing through a mail publishing rule, which automatically
sets up and configures a listener on the ISA server. A listener is an ISA component
that listens to a specific IP address and port combination for traffic, and processes that
traffic for the requesting client as if it were the actual server itself. For example, an OWA
listener on an ISA server would respond to OWA requests made to it by scanning them for
exploits and then repackaging them and forwarding them on to the OWA server itself.
Using listeners, the client cannot tell the difference between the ISA server and the OWA
server itself.
ISA Server is also one of the few products that has the capability to secure web traffic with
SSL encryption from end to end. It does this by using the OWA server??™s own certificate to
re-encrypt the traffic before sending it on its way. This also allows for the ???black box??? of
331
12
Securing Exchange Outlook Web Access with ISA Server 2006
SSL traffic to be examined for exploits and viruses at the Application layer, and then reencrypted
to reduce the chance of unauthorized viewing of OWA traffic.
Pages:
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550