On Wed, 29 Nov 1995, Brain 21 from GA Tech inquired:
> I am wondering if there is a firewall out there (perhaps most of them? I
> don't know) that will let me filter (IOW add my own rules) based on
> protocol AND specific bits and bit sequences.
There is at least one: FireWall/Plus.
> Ex. If I want to read a packet and disallow any packets where bits
> 161-169 are of the sequence 10000011 (loose source routing option) or I
> want to read the 8 bits of the "type" field in ICMP messages to filter
> out types of "destination unreachable" and "ICMP redirect."
Though seemingly out-of-place in a thread on Proxy API,
this example is easily accomplished using the Frame
Filtering firewall product we produce. FireWall/Plus
allows for both easy addition of customer filter (asked
below), *and* bit specific test criteria. Further, the
Filter Language allows for the creation of symbols that
define bit-groups located at specific location within a
frame, OR located in some *variable* location from frame
to frame.
The FireWall/Plus filters exist at each of the layers:
-> Application
-> Transport
=> Network Protocol
-> Frame
-> Packets on Ethernets
-> Tokens on Token Rings
To tie this remark to the thread: since each layer has
a set of filters, FireWall/Plus can accommodate the new
applications without the need for a corresponding proxy.
All that is required is a filter update to reflect the
desired level of protection when using a new application.
> I know that these examples are standard as far as rules or options
> already set up, but what if I want to make my OWN custom filters based on
> bits and sequences? Which firewalls is this possible with? FWTK? Socks
> proxies?
If my remarks above do not clarify what our product can
do in this area, please contact me directly. I'll try to
keep the product hype to a minimum! ;-)
Sincerely,
Ken Conquest
VP, Engineering
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