asynchronous_link was snort sees no fragmented attack

[Holger.Woehle () arcor net]

> Holger.Woehle () arcor net writes:
> ...i switched on the asynchronous_link but it doesn't change anything.
> I noticed that i cannot use the "flow" option even with asynchronous link...
> Snort 1.9 does not recognize the alarms declared with
"flow:to_server,established" .

> Chris Green <cmg () sourcefire com> writes:
> Well, in 1.9 w/ a 1.9 ruleset, you should turn on
>
> preprocessor stream4: asynchronous_link
>
> you are running into the state machines actually caring about the
> state of a TCP session which it can't ascertain w/o haivng both sides
> of the conversation.
>
> This is not related to fragmentation.
> --
> Chris Green <cmg () sourcefire com>
> A good pun is its own reword.

> Holger.Woehle () arcor net writes:
> echo "GET /aaaaaaa/aaa/aaaaa/aaaaaaaa/aaaaaaa/bcc/bin/ps" | nc
>
> The Sensor listens behind a Shomiti Ethernet TAP.
> May this be the problem ?  The Sensor only catches the
> "incoming" traffic. I do not want the answers from the machines.  Am
> i wrong with that ? Does snort neeed the outgoing traffic for defrag
> ?

i switched to snort 1.9 beta 2 and connected the sensor to both ends of the TAP
using device bond0.
Now i see all alerts!

But i don't want to inspect all outgoing traffic!

Do i need to abjust something according to use preprozessor
stream4:asynchronous_link ?
Do i need to configure preprozessor stream4_reassembly: client_only or something
else ?

cu
Holger








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