[Snort-sigs] Snort Rule Creation

John G drterdnugget at ...2420...
Tue Jan 31 18:57:55 EST 2017

Thanks for the help.  So i created a rule similar to that.  Wouldn't this
rule fire if the source ip address on any port communicates with those
destination addresses?  Attached is a screenshot of the rule I created.
However, the rule that i created will fire if it sees traffic on ports
80/443 from the one source address to 8 destination addresses on the same
ports.  What i want however is to alert if there is traffic outside of
those destinations.  Meaning, if source ip1 does connect with anything
outside of the 8 destination addresses, then alert.

alert tcp $SOURCEIP any -> ![destip1, destip2, destip3] any
(msg:”Unauthorized TCP traffic initiated”; flags:S; sid:1000000; rev:1;)

On Tue, Jan 31, 2017 at 5:09 PM, Joel Esler (jesler) <jesler at ...3865...>

> Maybe something like:
> alert tcp $SOURCEIP any -> ![destip1, destip2, destip3] any
> (msg:”Unauthorized TCP traffic initiated”; flags:S; sid:1000000; rev:1;)
> ?
> *--*
> *Joel Esler *| *Talos:* Manager | jesler at ...3865...
> On Jan 31, 2017, at 5:33 PM, John G <drterdnugget at ...2420...> wrote:
> Good Afternoon everyone,
> My name is John and I am starting out with creating Snort rules.  I have
> experience using Snort with IDS's such as Sourcefire and Security Onion for
> incident response.  However, i don't have much experience creating custom
> rules.  Although i once created a rule during one of my security classes
> during my undergrad program lol  Anyway, i have been reading documentation
> for how to understand/create rules from a variety of sources.  But I wanted
> to reach out to you guys and see what information you can provide.
> I have a device that is communicating with about 8 other devices.  I would
> like to write a rule that alerts if it detects any communication outside of
> those devices.
> Is it possible to list multiple ip addresses within a rule and maybe use
> an is not "!=" attribute.
> So something like: alert tcp != sourceip1  80 -> destip1, destip2,
> destip3, etc (msg:"Alert Message";)
> I would appreciate any assistance and will continue to do my own research
> and see if i can figure it out on my own :)
> Regards,
> John
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