What checks should I perform to ensure my router is malware free? This is for a home network
Checking a router for malware or tampering is tricky, as that would require being able to compare both firmware and configuration with known good versions. Comparing configuration could be done by comparing configuration backups, if the device has such functionality, but that doesn't really work for firmware. Therefore, there's no really sufficient way to ensure the router is free of malware.
However, some infections & router hijacks can be recognized from the modified behaviour in the network:
- Signs of man-in-the-middle (MITM) attacks (independent of which device is used).
- Reports from the ISP that the Internet subscription is used for malicious actions. If the router is infected, such actions likely continue despite there's no devices behind the router.
- as a part of distributed denial-of-service (DDoS) attacks
- for sending spam email.