Multiple Notifications of the same IP Ban
I'm currently using CrowdSec on my OPNsense firewall, and overall, it's been working very well. However, I've recently noticed multiple repeated ban notifications for the same IP range (89.248.160.0/21), which is known to be malicious. This has been occurring consistently over the past few days.
To mitigate this, I increased the ban duration from 4 hours to 72 hours, hoping it would reduce the repeated activity. Unfortunately, that hasn’t made a difference—similar IPs keep appearing.
I came across some information suggesting that CrowdSec bans don't necessarily block traffic entirely and that firewall-level blocking is needed to fully stop incoming connections. Since I'm using the CrowdSec plugin directly on OPNsense, I was expecting it to integrate with the firewall to block banned IPs.
How can I ensure that once an IP is banned by CrowdSec, it is completely blocked from attempting further connections?
Also, should I be concerned that the same IPs are persistently scanning ports on my network?
Thanks in advance for any advice.
17 Replies
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I am seeing similar thing on my opnsense box for that subnet as well. they have been hitting hard the past couple days. mainly 89.248.163.0/24 for me
My understanding is that since crowdsec watches firewall logs it will see the port scanning attempts even if they are blocked at the firewall level since they are logged regardless if they are allowed or blocked
also on opnsense crowdsec does block on the firewall level as long as the "Create blocklist rules" is checked in crowdsec settings or if you make your own on the wan interface
if it makes you feel better you can also enable the "Enable log for rules" option in the crowsec settings and then you can see the crowdsec blocks in the live firewall log in opnsense
Yeah it exactly what @Willpower says, unfortunately the default behaviour in the senses is to log every packet even if it was dropped by the crowdsec rules. This means it causes an echo chamber effect when an ip is blocked because of our rules but the engine doesnt already know this to be true. (cause the buckets / scenarios dont really care about previous stuff they are just attempting to monitor the current events)
You can as most do and that is putting a
GetDecisionsCount on the profile with your notification to report the first ban, but then dont send any notifications for the others but simply just increase the ban if you have an expression.Ya I see crowdsec is actively blocking those IP ranges and many others.
It's just that I have never received these many notifications from similar IPs before. So I feel a little insecure lol.
I don't know why but that range keeps on trying to hammer on my network. Daily over 100s of notifications with incremental ban time that I have now set.
Will they ever stop?
Some sites are just doing regular scans as a standard internet scanning per vulnerability discovered
I’m still getting hammered here too. Same ranges
In that case I suggest adding permanent block in firewalls/routers
What I did was create a firewall alias with the spammy ips, added a block rule (above the crowdsec one), and disabled logging for that rule only so it doesn't trigger any more alerts 🙂
It seems to have stopped as of today.
I have one and only one IP is spamming my logs.
It's installed on my pfSense.
After that monthly alert quota exhausted
One IP X one type of attack
Would like to ban permanently.
Just add another rule befor corwdsec firewall and add it there to drop the traffic, or make it in similiar way as crowdsec does it - via ipsets taken from files and update the file content
Please teach me. I only followed the instruction how to deploy it
https://docs.crowdsec.net/docs/getting_started/install_crowdsec_pfsense/
pfSense | CrowdSec
We have created a pfSense package with
Refer to pfsense manual, i dont remember how it is done in pfsense
If you ads a rule with explicilty defining ip addresses then that rule may be limited to say 8 addresses, with reference from a file it is usually capable of having hundreds of them in the file
Should I use Fail2Ban or any alternatives along with CS?
It is for you to decide, generally crowdsec has rules such as fail2ban
Or you can extend fail2ban to send an event to corwdsec