Can we get snort to differentiate between client and server?

[Jason Haar <Jason.Haar () trimble co nz>]

Check out this false-alert generator:

alert tcp $EXTERNAL_NET any -> $HOME_NET 12754 (msg:"DDOS mstream client to
handler"; content: ">"; flags: A+; reference:cve,CAN-2000-0138;
classtype:attempted-dos; sid:247; rev:1;)


What happens is one of the $HOME_NET servers makes a TCP connection to a
remote server. That could be a SMTP, Web, whatever. It *happens* to use port
12754 as the client port -  contains ">"  - and the rule is triggered.

Shouldn't snort "think" in left-to-right? i.e. 

host1 port1 -> host2 port2

means

if host1 *instigates* a connection to host2, then...

At the moment, host1 could be either the server or the client.

Shouldn't this be changed, or a new option of "directional" be added which
does the same thing? Tonnes of potential false alarms would drop out of the
loop. 

-- 
Cheers

Jason Haar

Unix/Special Projects, Trimble NZ
Phone: +64 3 9635 377 Fax: +64 3 9635 417

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