Monitoring usage

Hi Folks - I'm a Mac user, with a MacBook Pro, iMac, iPhone and iPad all using my local wifi quite happily.

Even when all this stuff is switched off (and I mean off, not just idle or on standy) the flashy lights on my cable modem and adjoining router still blink away merrily with no discernible pattern. I have got the system securely passworded with a word no one is likely to guess or find by accident, but am still suspicious that it's being used by someone locally. Or is that just what it does whilst searching for someone to communicate with?

Grateful for your comments please.

What type of security are you using? WEP or WPA? If WEP then it's trivial to crack these days so someone could have found the security key. Even WPA is breakable.

I'd suggest chnging the password nd seeing if the problem goes away - at least temporarily.

You are seeing the very common phenomenon of Internet Background Noise.

Basically, there is a small amount of traffic hitting your IP that is unsolicited - it could be people running port scans, virus / worm traffic looking for new victims, traffic hitting your IP from another previous user of that IP (such as you getting the dynamic IP of someone who runs torrents and machines attempt to connect back to the IP expecting the last guy to be there).

There is also a small amount of local subnet broadcasting going on on each VM segment as users power on and off their modems - yours will appear to be responding too.

In short, it's completely normal and to be expected - nothing to worry about what so ever.

Thanks to you both for your replies, and sorry I've been away for a while and not replied before.

I do already have a very strong WPA password, so thought it very strange that it could have been broken but I'll change it anyhow as suggested by ionic, and am grateful for Pete's interesting explanation of other things that happen that most users are completely unaware of.

It's really good that such clever, helpful people are on here.