Text 3427, 36 rader
Skriven 2005-04-06 21:33:04 av Chris (1:379/45)
   Kommentar till text 3426 av Gary Britt (1:379/45)
Ärende: Re: Wireless Network Security Questions
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From: Chris <nospam@noemail>

SPI = Stateful Packet Inspection
http://www.webopedia.com/TERM/S/stateful_inspection.html


  Also referred to as dynamic packet filtering. Stateful inspection is a
firewall architecture that works at the network layer. Unlike static packet
filtering, which examines a packet based on the information in its header,
stateful inspection tracks each connection traversing all interfaces of the
firewall and makes sure they are valid. An example of a stateful firewall may
examine not just the header information but also the contents of the packet up
through the application layer in order to determine more about the packet than
just information about its source and destination. A stateful inspection
firewall also monitors the state of the connection and compiles the information
in a state table. Because of this, filtering decisions are based not only on
administrator-defined rules (as in static packet filtering) but also on context
that has been established by prior packets that have passed through the
firewall.

As an added security measure against port scanning, stateful inspection
firewalls close off ports until connection to the specific port is requested.

Check Point Software is credited with coining the term stateful inspection in
the use of its FireWall-1 in 1993.

Gary Britt wrote:
> What is SPI?  The router has the ability to examine every packet coming in
> on the WAN/Internet side and determine something about its authenticity or
> something, discarding suspicious packets.  They call it SPI.  It also has a
> basic defense for DoS attacks.  Both are turned off by default.  I know what
> a DoS attack is, but not sure what SPI is or why I would want it or the
> performance implications of using it.

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