[SOLVED] Do not log TCP packets with flags TCP:RA / TCP:PA etc.

m0urs

If I enable logging for the default blocking rule, packets with TCP:RA/TCP:PA etc. flags will also be logged. I guess these packets can be safely ignored.

So I want just to see packets with the SYN flag set to be included in the logs. Because these packets might be something which is unintentionally blocked and might need my attention, right?

I tried to create a new blocking rule at the end of all other rules with logging enabled and played a bit with the TCP flags setting. Unfortunately I did not yet find the correct setting for "TCP flags" ignore all these packets with TCP:RA/TCP:PA etc.

Could someone give me a hint how I can do that?

Thanks a lot,
Michael

bmeeks

You can't do this by directly editing the default rule, but you can achieve the result this way.

Disable logging of default rules, then create your own clean-up rule with logging enabled. While creating the rule, follow the steps below.

You can do what you wish by using the Advanced Flags section when editing or creating a rule:

To access this option, scroll down to the Advanced Options section when editing a rule and click the button to view the options. From there scroll down to find the TCP flags and check the ones you wish to use.

I do the same as you want. I only log SYN attempts on my WAN. That cuts down on the noise. The only downside is this can hide stuff that might be useful when troubleshooting, so if you ever are trying to figure out why something is not working but you're not seeing anything logged on the firewall, you would want to temporarily disable this option so you get everything logged.

johnpoz

Same here, I have default deny logging off, and only log syn that hits my wan.. And then have another log rule for udp on ports that might be of interest..

The net is pretty noisy place - trimming down the log to only interesting info keeps it a bit less noisy.

mcury

@johnpoz said in Do not log TCP packets with flags TCP:RA / TCP:PA etc.:

Same here, I have default deny logging off, and only log syn that hits my wan.. And then have another log rule for udp on ports that might be of interest..

The net is pretty noisy place - trimming down the log to only interesting info keeps it a bit less noisy.

hmmm, interesting.. How I didn't think about this before ??!

Edit:
In my case, for both WANs, last 5 days, very little noise:

NOT pf_tcp_flags:S AND source:filterlog[*]: AND (pf_interface:ix2 OR pf_interface:ix3) AND pf_ipv4_protocol:tcp

johnpoz

@mcury said in Do not log TCP packets with flags TCP:RA / TCP:PA etc.:

How I didn't think about this before ??!

That is a good question, how long you been working with firewalls? @bmeeks has been in the field for many many a year ;) hehe And myself as well.. When you have to look at logs of this stuff, you look for ways to clean them up and only have stuff your interested in ;)

mcury

That is a good question, how long you been working with firewalls? @bmeeks has been in the field for many many a year ;) hehe And myself as well.. When you have to look at logs of this stuff, you look for ways to clean them up and only have stuff your interested in ;)

More than 10 years, I guess I'm used to suffer when checking logs

johnpoz

@mcury 10 years - just a baby then, heheh that does look pretty quiet - that is just non Syn traffic looks like. What about UDP noise? You doing any filtering by source IP that your not logging?

I block most if not all of the scanners, like shodan, etc. I also limit traffic by geoip on who can actually hit my port forwards.. Now I currently log all this traffic, if it is syn only..

There are multiple was to reduce the noise that is logged..

mcury

@johnpoz said in Do not log TCP packets with flags TCP:RA / TCP:PA etc.:

10 years - just a baby then

Yeap, I started with Cisco routers and switches and around 15 years ago, and around 10 years ago it was just firewalls, Cisco ASA, Fortigate, Checkpoint, Palo Alto and Sonicwall, never looked back but we never forget the routing stuff =)

@johnpoz said in Do not log TCP packets with flags TCP:RA / TCP:PA etc.:

that is just non Syn traffic looks like.

In the pic above, I was just filtering just TCP, but excluding SYN.. let me include UDP in it. Here it goes:

@johnpoz said in Do not log TCP packets with flags TCP:RA / TCP:PA etc.:

What about UDP noise? You doing any filtering by source IP that your not logging?

Edit: Logging all TCP but TCP:S and all UDP traffic that hit both WANs, disabled packets that are blocked by the implicit default block rule.

johnpoz

@mcury said in Do not log TCP packets with flags TCP:RA / TCP:PA etc.:

and all UDP traffic that hit both WANs

You might want to limit that to interesting ports if your goal is trim down the amount of noise your logging. My interesting ports is a pretty long list, but it does reduce some of the noise not logging every port ;)

mcury

@johnpoz said in Do not log TCP packets with flags TCP:RA / TCP:PA etc.:

You might want to limit that to interesting ports if your goal is trim down the amount of noise your logging. My interesting ports is a pretty long list, but it does reduce some of the noise not logging every port ;)

I'll start preparing that list now.. =)

johnpoz

@mcury here is my list.. It prob way longer than need/should be but I had does some looking to what ports to put in there while back..

2:3 Entry added Thu, 17 Oct 2019 06:17:40 -0500
7 Entry added Thu, 17 Oct 2019 06:17:40 -0500
9 Entry added Thu, 17 Oct 2019 06:17:40 -0500
13 Entry added Thu, 17 Oct 2019 06:17:40 -0500
17 Entry added Thu, 17 Oct 2019 06:17:40 -0500
19:23 Entry added Thu, 17 Oct 2019 06:17:40 -0500
37:38 Entry added Thu, 17 Oct 2019 06:17:40 -0500
42 Entry added Thu, 17 Oct 2019 06:17:40 -0500
49 Entry added Thu, 17 Oct 2019 06:17:40 -0500
67:69 Entry added Thu, 17 Oct 2019 06:17:40 -0500
80 Entry added Thu, 17 Oct 2019 06:17:40 -0500
88 Entry added Thu, 17 Oct 2019 06:17:40 -0500
111:113 Entry added Thu, 17 Oct 2019 06:17:40 -0500
120 Entry added Thu, 17 Oct 2019 06:17:40 -0500
135:139 Entry added Thu, 17 Oct 2019 06:17:40 -0500
158 Entry added Thu, 17 Oct 2019 06:17:40 -0500
161:162 Entry added Thu, 17 Oct 2019 06:17:40 -0500
177 Entry added Thu, 17 Oct 2019 06:17:40 -0500
192 Entry added Thu, 17 Oct 2019 06:17:40 -0500
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207 Entry added Thu, 17 Oct 2019 06:17:40 -0500
217 Entry added Thu, 17 Oct 2019 06:17:40 -0500
363 Entry added Thu, 17 Oct 2019 06:17:40 -0500
389 Entry added Thu, 17 Oct 2019 06:17:40 -0500
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434 Entry added Thu, 17 Oct 2019 06:17:40 -0500
443 Entry added Thu, 17 Oct 2019 06:17:40 -0500
445 Entry added Thu, 17 Oct 2019 06:17:40 -0500
464 Entry added Thu, 17 Oct 2019 06:17:40 -0500
497 Entry added Thu, 17 Oct 2019 06:17:40 -0500
500 Entry added Thu, 17 Oct 2019 06:17:40 -0500
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512:515 Entry added Thu, 17 Oct 2019 06:17:40 -0500
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682:689 Entry added Thu, 17 Oct 2019 06:17:40 -0500
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767 Entry added Thu, 17 Oct 2019 06:17:40 -0500
772:776 Entry added Thu, 17 Oct 2019 06:17:40 -0500
780:782 Entry added Thu, 17 Oct 2019 06:17:40 -0500
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989:990 Entry added Thu, 17 Oct 2019 06:17:40 -0500
996:1001 Entry added Thu, 17 Oct 2019 06:17:40 -0500
1007:1008 Entry added Thu, 17 Oct 2019 06:17:40 -0500
1012:1014 Entry added Thu, 17 Oct 2019 06:17:40 -0500
1019:1051 Entry added Thu, 17 Oct 2019 06:17:40 -0500
1053:1060 Entry added Thu, 17 Oct 2019 06:17:40 -0500
53 Entry added Thu, 17 Oct 2019 12:07:49 -0500
123 Entry added Sat, 11 Apr 2020 02:33:04 -0500
33434 Odd port from pfsense forums

Wow from 2019, man time flies.. Doesn't seem like that long ago that I did that ;)

m0urs

@bmeeks
Unfortunately it seems not to work that way. I still get packets logged with these flags set:

Do not get confused, I named my self created rule "Default blocking rule", but the ID is my own rule and not the pfSense default rule.

Here is the rule I created:

What am I doing wrong?

mcury

@johnpoz Wol, that is indeed a long list, I was thinking about ports:

7 WOL common used
9 WOL default
53 DNS
67:68 DHCP
80 QUIC
88 Kerberos
123 NTP
443 QUIC
500 IPsec
514 Syslog
1194:1198 Common OpenVPN ports..
4500 NAT-T

mcury

@m0urs said in Do not log TCP packets with flags TCP:RA / TCP:PA etc.:

What am I doing wrong?

Did you disable this ?

johnpoz

@mcury yeah its a bit long.. I went a bit overboard when was looking into ports that might be good to log.. I could prob trim it down.. But I really don't see much udp traffic even with that long list.

Yeah default deny logging is off

m0urs

@mcury said in Do not log TCP packets with flags TCP:RA / TCP:PA etc.:

Did you disable this ?

Yes.

As I said: The logging comes from my own created rule and not from the pfSense default blocking rule.

mcury

@m0urs said in Do not log TCP packets with flags TCP:RA / TCP:PA etc.:

The logging comes from my own created rule and not from the pfSense default blocking rule.

I'm trying to replicate this here, but now filtering TCP:S only, in my LAN networks.

mcury

Are you using that "Invert match" option for source or destination in that rule ? So far, I'm unable to replicate this behavior here but I'm not using those options.

m0urs

@mcury No, I do not use "Invert Match". That is my definition, together with that TCP Flags option mentioned above:

m0urs

@mcury ah, maybe this does not work if protocol set to "Any"? I will try with Protocol set to "TCP" ...