Bad Hug! Bad Hug!
Operation WrtHug is the name given to a current campaign that has infected a large number of older ASUS WRT routers and is looking for more to take over. The campaign leverages four flaws including both command injection and command execution vulnerabilities on eight ASUS WRT routers, which Bleeping Computer lists here. The routers are all older, and some of them are EoL. ASUS released patches for these vulnerabilities some time ago, so it is worth checking to see if there is a new version of the firmware for your router.
If there is not an update for your router, your best bet is to toss it and get a newer model. That way you can experience all new and undiscovered security threats … or hope you managed to find a rare secure router. If you can’t toss the old ASUS WRT router, at least disable remote access features and the AiCloud feature as well.