As I understand it, the internet LED is solidly lit when all of your devices are turned off, however, occasionally you see the internet LED blinking as though traffic is passing over your connection - am I correct?
First, check the router's log as it may give you a clue to whether someone has hacked into your connection. You could also check under Attached Devices and verify that all the MACs are yours. (An inventory list of all your MACs is a useful thing to always have).
Also, once you ensure that your router is properly configure with the highest security, a good strong passphrase, and that you have also changed the default admin password, you should be safe from all but the most skilled hackers.
On some routers, it is normal for the internet LED to blink even when all your devices are off. This is normally cause by other servers on the internet checking to see if website pages are up-to-date on your PCs. You should check you router's online PDF manual to see if this is normal for your router.
One more thing may cause your lights to blink are attempts to connect to your network. These may just happen unintentionally, since most devices will just try to connect to the strongest signal they "see". You can try turning off SSID broadcast, which should prevent most Windows machines from detecting your network and trying to connect. This is not foolproof of course, but is just another means of minimising nuisance attempts to connect to your network.
internet light will continue to blink regardless of any background application which may communicates.
if you unplug all the devices from the router and turn off the wifi devices and see internet right is blinking are any of network scanning from any network user on the internet or other networking devices like ISP with continues communicating , pinging etc.
generally speaking you will not going to see internet light not to blink.
if you have any ports open on router and even it's LAN device is off, some network scan from the internet may try to gain access on other way to look at it.
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