r/security • u/sztupy • 15m ago
Security Operations Keep getting SSH probing login attempts from the ISPs router
I am a Vodafone UK broadband user and use their Router/Modem to connect to the internet. The router does provide a public IPv4 address, but no DMZ/port forward is configured.
I also have a few Linux machines in the internal network, both desktop and server. They are internal, and are not meant to be accessed from the outside Internet. As mentioned the router doesn't have any port forwarding enabled.
What I started to see is that around every 30 minutes all of the Linux machines on my network get SSH login attempts coming from 192.168.1.1 - the router's IP address. They look to be brute force login attempts trying out multiple username/password combinations, e.g.:
sshd-session: Invalid user admin from 192.168.1.1 port 35562
sshd-session: Invalid user default from 192.168.1.1 port 35566
sshd-session: Invalid user admin from 192.168.1.1 port 35570
sshd-session: Invalid user weblogic from 192.168.1.1 port 35494
sshd-session: Invalid user redhat from 192.168.1.1 port 35496
sshd-session: Invalid user developer from 192.168.1.1 port 35498
sshd-session: Invalid user public from 192.168.1.1 port 35500
sshd-session: Invalid user student from 192.168.1.1 port 35502
This starts every 30 minutes, and keeps on going for 10-20 minutes. Obviously/fortunately all of the attempts fail. I did install an ssh honeypot in the system to see what would happen if they would get in, but all it does is disconnect from SSH, then start the retry in exactly 30 minutes.
When I first saw these attempts I got shocked a bit, as I thought I have a compromised system in the house, but then after checking it get really odd for me that all requests originate from 192.168.1.1 - the router.
I am a bit stuck here, as I don't really know what's up and how worried I should be. Do I have a compromised system that spoofs the IP? Does the router do some weird NAT translation for a compromised device that's in my network? Or does the router itself do these ssh attempts? Would these probing attempts be a lame part of Vodafone's Secure Net Home?
Tried searching the web for any of these, but couldn't really find anything specific that matched my criteria.