Helping people with computers... one answer at a time.
Many applications that you run and even some websites that you visit can inadvertently expose your online status to your friends.
I find that whenever I log onto the internet, a certain unwelcome friend immediately knows that I am online. How can I stop this? Can it be done through my ISP?
It doesn't really have anything to do with your ISP, but more likely, it's the software that's running on your machine.
Software that essentially says, "I'm here!" as soon as you connect.
I'll look at the most likely causes.
You probably already thought of this, but I need to include it to be complete. If your friend is connected to you in any way via an instant messaging program or service like Windows Live Messenger, Yahoo Instant Messenger, Google Talk, Skype, or any of several other services, then the very nature of these programs shows your online status by default.
Depending on which service you use, there are several approaches to improve your privacy:
Don't run the program by default; run it only when needed.
Make sure that the program is configured to show you as online only to your friends (and of course, make sure that this person isn't one of them).
If the program supports it, set your status to "stealth," which hides your visibility online.
In short, use the options of the instant messaging program to hide your online status from those that you don't want to see.
If you login to Gmail on the web, you may also be enabling Google's chat feature or Google Talk.
Friends and contacts may then be able to see your online status if they're using the same service.
You can select Invisible as your status to hide yourself. Or in the Chat section on Gmail's Options page, you can turn chat off.
Then you may also be unwittingly showing your online status to your friends by virtue of Facebook's chat feature.
Facebook has a chat feature built in that many people don't actually know about. It defaults to being enabled and will show your online status to at least your friends and possibly more.
The solution is relatively simple here as well. Click Chat in the lower right corner. Click the Options gear icon and select Go Offline.
Remote access tools, file sharing tools, and others may make your presence online visible as a side effect of what they do.
There's no complete list, but it's worth reviewing all of the software currently running on your machine - particularly software that you might have in common with this "friend" of yours - to see if you might inadvertently be exposing your online status.
If so, examine that software for options to hide that or perhaps choose not to run the software at all.
Also for completeness, there's always the possibility that the person you're concerned about has installed some form of malware or spyware on your machine.
Malware can do anything - including reporting your online status if that's what the malware author wanted to do.
Make sure that you're running up-to-date anti-malware tools and as always, know how to practice safe computing.