Re: Triggering inspector rules (arp_spoof / stream)

Here are the steps to enable the Stream_Inspector preprocessor and rule 1 in Snort3:

Open your Snort3 configuration file (usually located at /etc/snort/snort.conf) in a text editor.
Search for the section that starts with "preprocessor stream_inspect".
Make sure that the "stream_inspect" preprocessor is enabled by removing the "#" character at the beginning of the line.
To enable rule 1 of the Stream_Inspector preprocessor, add the following line to your Snort3 configuration file:
stream_preprocessor: rule 1
Save the configuration file and restart Snort3 for the changes to take effect.
Once rule 1 of the Stream_Inspector preprocessor is enabled, it should trigger an alert when it detects a TCP SYN flood attack. The exact threshold for this rule can be adjusted by modifying the "max_queued_packets" option in the Snort3 configuration file. By default, this option is set to 5 packets in a 1-second window, but you may want to adjust this value depending on the specifics of your network environment.

Sent from my iPhone

> On Apr 10, 2023, at 6:05 AM, Julia Geiger <[email protected]> wrote:
> 
> Hello Snort Community,
> 
> I am a student who just started working with Snort3 (Version: 3.1.18.0).
> For my Project I need to detect arp spoofing and TCP/SYN flood attacks.
> 
> For the arp_spoof inspector I configured the ip/mac address mapping in the configuration file.
> I also wrote rules for the four arp_spoof inspector events.
> When I run an arp spoofing attack I get a log entry for rule 4 "attempted ARP cache overwrite attack".
> But when a message is sent to a host were the destination ip/mac address is spoofed, I do not get a log entry for rule 3.
> I looked at the send packages and the ip/mac address do not match the configured values. I do not know why these rules are not triggered.
> My config looks like this (inside of my snort.lua file):
> arp_spoof = {
>    hosts = {
>        {ip ="x.x.x.x", mac ="xx:xx:xx:xx:xx:xx"},
>    }
> }
> 
> My rule file looks like this:
> alert (msg: "some msg1", gid: 112; sid: 1;)
> alert (msg: "some msg2", gid: 112; sid: 2;)
> alert (msg: "some msg3", gid: 112; sid: 3;)
> alert (msg: "some msg4", gid: 112; sid: 4;)
> 
> 
> Besides that I am trying to trigger rule 1 of the stream_inspector to detect SYN flood attacks.
> I looked into the code but I could not find what the conditions are to trigger the rule.
> But so far I could not trigger this rule.
> My own rule which just counts incomming packtes with "flag:S" works perfectly though.
> I again enabled the inspector in my config and wrote rules for that event.
> 
> My config looks like this (inside my snort.lua file):
> stream = {}
> My rule file looks like this:
> alert (msg: "msg1"; gid: 135; sid:1;)
> 
> 
> I would really appreciate any support on triggering these events.
> 
> Thanks for any advice!
> 
> 
> Best regards
> Julia
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