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I heard that your PC can get infected just by connecting to the Internet (even without the web). Assuming I'm connected to a private home network, how can an attacker tell that I just connected to the Internet if I'm not browsing the Internet or doing something else that requests information from a server on the Internet? Is my PC publicly announcing that it connected to the Internet? How can I prevent an attacker from finding my PC on the Internet?

closed as unclear what you're asking by Steffen Ullrich, Xander, Neil Smithline, RoraΖ, Dog eat cat world Dec 2 '15 at 7:49

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    The linked question explains: the attackers do not know that you have connected to the Internet, they connect to your Internet-facing connection (normally a router), or your computer if you are not behind another connection, like is the case on public wifi. – schroeder Nov 29 '15 at 4:50
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  • I heard that your PC can get infected just by connecting to the Internet (even without the web).

Note that the source you linked does not say you can get infected by connecting to the Internet, but if you're connected to the Internet. Connecting to the Internet does not trigger an attack, it just opens the door for it.

  • Assuming I'm connected to a private home network, how can an attacker tell that I just connected to the Internet if I'm not browsing the Internet or doing something else that requests information from a server on the Internet?

S/he can't, and doesn't need to. Active attacks are continuously and blindly sent to all IP addresses without bothering to check who if anybody is connected. The moment you connect to the Internet these attacks start arriving at your border router.

  • Is my PC publicly announcing that it connected to the Internet?

Possibly, in many ways, depending on what exactly you mean by "publicly". For example, it may automatically register with Skype, Teredo, DynDNS or Dropbox, query several software vendors for updates or post your online status to WhatsApp. But none of these is known to draw attacks to it.

  • How can I prevent an attacker from finding my PC on the Internet?

Wrong question. The attacker does not look for your PC. S/he just attacks everything that is connected, and if your PC happens to be there it will be attacked. No finding involved.

  • I linked the source to the question – Jorge Luque Nov 29 '15 at 2:30
  • I amended my answer to take that into account. – Tilman Schmidt Dec 2 '15 at 0:39
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I read that your PC can get infected just by connecting to the Internet (even without the web).

I think you're referring to bots that automatically attempt to infect random computers around the world. If you're using an unpatched older operating system, then this is definitely possible. Heck, it's possible with a newer unpatched operating system, though less likely.

When I set up a test Windows XP box, it was hacked immediately upon connection to the internet. I got unlucky.

Assuming I'm connected to a private home network, how can an attacker tell that I just connected to the Internet if I'm not browsing the Internet or doing something else that requests information from a server on the Internet?

If you're using Windows, your box is requesting information from the "internet." However, this isn't needed by an attacker: a simple mass scan of random IP addresses can "get" you, and anyone else who is vulnerable. Here's an example:

Let's say your IP address is 76.101.124.1. A mass scanner could simply scan 76.101.124.*, and attempt to send malicious data over the network. Maybe they've found a way to exploit typical windows services which are listening, and they're attempting to mass-infect this way. They don't necessarily know who you are. As Tilman said, they're blindly attempting to infect random machines on the internet.

Is my PC publicly announcing that it connected to the Internet?

Are you using Windows? Then yes, yes it is. It's attempting to connect to a Microsoft server to check for updates, and to check for internet connectivity.

Are you using a version of Linux that is capable of updating? Then yes, it is connecting to the internet to check for updates, and possibly to phone home (Ubuntu).

Both Windows and Linux do the same thing in general. Phone home / connect to updater services. But you're being needlessly worried about it, and it isn't something that should affect you negatively unless there's a vulnerability in the updating programs.

How can I prevent an attacker from finding my PC on the Internet?

You could block all incoming and outgoing connections, but I suspect this would be quite detrimental to your experience. Otherwise, you should just patch as soon as possible to limit your potential attack space.

  • I linked the source to the question – Jorge Luque Nov 29 '15 at 2:32

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