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Could my computer be compromised if someone knew my external IP? I know that when you type that in it just goes into the router page, but my computer is connected to said router.

If so, what is the attack vector? How can I protect myself?

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closed as too broad by Adnan, Xander, Manishearth, NULLZ, Iszi Oct 30 '13 at 14:15

There are either too many possible answers, or good answers would be too long for this format. Please add details to narrow the answer set or to isolate an issue that can be answered in a few paragraphs.If this question can be reworded to fit the rules in the help center, please edit the question.

2 Answers 2

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Your external IP isn't technically your machine's external IP, it's your router's external IP. So your machine wouldn't directly be the target of any attack: your machine doesn't have an external IP.

Instead, attacks would be targeted at your router. The success on that front depends on your router. Some are quite secure, some are known to be horribly broken. Search for your router's product name online to see what people have to say about it.

If your router can be broken, then the attacker could use it as a stepping-stone to get to your computer and all other computers on the network.

Another possible vector is forwarded ports. If your router is configured to forward traffic on a specific port to your computer (either manually configured by you or automatically configured through UPnP), then any attacks that use that specific port will be forwarded to your computer as well. If your computer is running a vulnerable service on that port, then that could prove problematic for you.

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The first sentence is misleading and borderline incorrect. In many cases it can be correct, but it's not the rule. Actually, in my building, everybody's machine's IP is their external IP. I use the same IP assigned on my eth0 to SSH to my home computer from my work computer. –  Adnan Oct 30 '13 at 12:19
    
@Adnan The question explicitly states that the IP address goes to his router. Your own personal situation is different, and therefore not applicable here. –  tylerl Oct 30 '13 at 20:49
    
It appears I haven't noticed that part in the question. However, I'd like to note that most home routers have a DMZ option that, when activated, exposes all ports of the DMZ host on the external IP, effectively rendering that external IP to the IP of the internal host. –  Adnan Oct 30 '13 at 21:27

If you turn off remote management in your router and are not forwarding any ports then you won't have much of an attack vector unless there is a serious flaw in your router's firmware. The router would prevent any traffic from getting into your computer. Someone could potentially DDOS your router but that would only cause it to stop being able to accept new packets, they wouldn't be able to by-pass it.

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