Because the firmware-update process varies from one make and model to another, here's a quick, generalized overview -- one that's based on upgrading an Asus WRT router.
Step i: Visit the Asus support site and download the most current firmware for your specific model.
Needless to say, you'll lose all internet connectivity while this is happening.
According to a new report from security firm Cisco Talos, the VPNFilter malware is "targeting more makes and models of devices than initially thought, and has additional capabilities, including the ability to deliver exploits to endpoints." That means if you own one of the affected routers -- and that list has expanded to include models from Asus, D-Link, Huawei, Ubiquiti, Upvel and ZTE -- it's strongly recommended that you perform two key steps: upgrade the firmware and then factory-reset the router. Of course, if you've never so much as looked at that dashboard, well, it may be time for a trip to the owner's manual -- or the router manufacturer's online help pages.
In some ways this is the easier step, as it can often be done within the confines of your router's dashboard.
If you never changed the defaults, you should be able to find them in the instruction manual.
(Often, the defaults are "admin" and "password," respectively.) Step iii: Click the Administration button (again, this is just for Asus routers; on other models it might be Configuration or Firmware or the like), then the Firmware Upgrade tab.