A router that is facing the Internet is one of the most important devices in your network. If it gets compromised, the attackers are able to intercept all network traffic, reroute it, launch attacks on resources inside your network infrastructure and eventually compromise servers and workstations inside your network.
VPNFilter is a trending malware that leverages weak security configuration of the router. It is associated with activity of famous APT group APT28 or Fancy Bear. There are great write-ups on this topic from Cisco Talos, Fortinet and other companies. So, if you want to know how VPNFilter works, just read them.
Apart from VPNFilter there has been an overall interest increas to vulnerabilities in routers among APT groups and hackers. Since 2017 there has been 6 zero-days in network devices of the following vendors:
https://www.zero-day.cz/database/499/ - Used to change DNS settings of the affected routers against users in the UK.
https://www.zero-day.cz/database/493/ - used in a targeted attack in Czech republic.
https://www.zero-day.cz/database/488/ - used in Slingshot APT campaign
https://www.zero-day.cz/database/480/ - used by Mirai and Satori botnets
https://www.zero-day.cz/database/469/ - shipped with a backdoor. The vendor was compromised.
https://www.zero-day.cz/database/455/ - used to mine cryptocurrency.
How to protect yourself
In the meantime, we would like to provide basic recommendations on how to protect your router from similar attacks.
All default credentials on the routers should be changed.
The latest available firmware should be installed. If your router is no longer supported by the vendor, replace it.
All management router interfaces should not be accessible from the Internet. Run an external scan to see which ports are open. You can do this for free via our trial package. Just register, run the scan and see the results. Your router can be considered secure if the report returns empty or without any router management port in it (in case you host services behind the router, only these services should be accessible).
Use firewall to deny access to all open management ports and re-run the scan to confirm that the ports are not accessible from outside.