[Snort-sigs] Snort Rule Creation

Joel Esler (jesler) jesler at ...3865...
Tue Jan 31 20:57:50 EST 2017


You know you can do ![80,443] as ports right?

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On Jan 31, 2017, at 8:50 PM, John G <drterdnugget at ...2420...<mailto:drterdnugget at ...2420...>> wrote:

That is from Sourcefire.  This is what the actual rule looks like now.

alert ip !Source address any <> [All, 8, destination, addresses] any (sid:1000000; gid:1; msg:"Unwanted Traffic"; classtype:tcp-connection; rev:5; )

The rule should work right?   Might be an issue with the way our network is setup and where our ids is located.

On Tue, Jan 31, 2017 at 7:41 PM, Desmond Agee <dezmondagee at ...144...<mailto:dezmondagee at ...144...>> wrote:
What program is that a snap-shot of?

Desmond Agee

On Jan 31, 2017, at 8:27 PM, John G <drterdnugget at ...2420...<mailto:drterdnugget at ...2420...>> wrote:

Alright, so this is basically what I did.

Alert ip !SOURCEIP any [8, Destination, IP's] any (msg:"Unauthorized TCP traffic initiated";)

I figured out that you can negate with ! in front of the IP's.  To test it, I have been sending ping packets to the destination IP's from a source ip address that is NOT what i entered in the Source IP part of the rule.  However, I am not receiving any alerts.  Do i need to add arguments to look for tcp traffic?

On Tue, Jan 31, 2017 at 5:58 PM, John G <drterdnugget at ...2420...<mailto:drterdnugget at ...2420...>> wrote:
Forgot to attach the screenshot.

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

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

?


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Joel Esler | Talos: Manager | jesler at ...3865...<mailto:jesler at ...3865...>






On Jan 31, 2017, at 5:33 PM, John G <drterdnugget at ...2420...<mailto: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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