Question for qualified telecom tech please ?

I have the telephone and the internet services from the same provider.

Both the computer and the telephone (with the appropriate filter) are connected to a line splitter and then into a wall jack.

It's been 3 times in a few months the LED on the phone comes on for a few seconds while surfing even though there is no ingoing or outgoing call.

Is it possible for some malware to activate the telephone the way the hardware is connected ?

Or what else could cause the LED to come on when the phone is not in use ?

I'm an IT professional myself but this is a little out of my league. Knowledgeable answers please.