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Suppose an enemy has obtained the IP address of my home computer, and communicated this fact to me in an attempt to threaten/blackmail me.

What exactly are my risks, and how can I minimize them?

My OS is Windows Vista, and my ISP is Verizon.

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up vote 5 down vote accepted

Your router firewall will likely protect you from anything except a denial of service attack (your vendor may have some defenses against this). Make sure you haven't opened any ports needlessly. Rebooting your router may trigger an assignment of a new IP address.

Contact your ISP and let them know that there's been a threat and to ask them what they can do and what you should do. While law enforcement won't be able to do anything yet, you may be able to file an informational report with them to document what's occurring.

By the way, if this person "knows" that your IP address is in the range 192.168.. or 10...* then don't worry. These are private ranges that are not routable of the internet. Your PC will be assigned an address in this range which can only be reached by the router and other computers, if any, on the same local segment.

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As Dennis suggested, a person knowing your IP address means little (especially if they don't now what to do with it). Since it is unlikely that you have a statics IP address do as Dennis suggested and unplug your modem and router for a bit, then plug them back in and try to force a new IP. You could also just call your ISP and ask them to re-provision your modem, which would also get you a new IP. I wouldn't loose any sleep over it though :) – ubiquibacon Mar 7 '11 at 1:55
Even if your IP is static, they would need to spend time probing for any openings (which most routers don't have by default, you have to open up all the ports yourself) and then there would have to be something to exploit within that opening (such as a badly setup http server for example). In any case, as mentioned by others, you really only need to worry about a DOS attack, which is difficult to do these days without a lot of other helpers. – MaQleod Mar 7 '11 at 3:40

Not much. FYI: Your public IP is visible to every server you connect to online.

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Unless you've done something blatently illegal, there should be nothing to worry about.

Most ISPs give you a dynamic IP address which changes occasionally, so your enemy would have to know what your IP was at a particular point in time to be able to trace any activities back to your computer. You can attempt to get a new IP assigned by issuing the following in a command window:

ipconfig /release
ipconfig /renew
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That command will trigger assignment for the PC, but won't affect the public IP address of the router. You would need to use the router's administrative interface (web page) or simply reboot the router (by power cycling it). It's not unheard of, however, to receive the same IP address. – Dennis Williamson Mar 7 '11 at 1:36
Ah, you're correct. Reboot the router/modem to try to force a new IP address. – cantfork Mar 7 '11 at 3:32
Rebooting the router won't always work, as many ISP's DHCP lease is typically 24 hours, meaning that you'd either have to restart your router at the right time, or just leave it disconnected for a bit over a day. Lease times can be from an hour to a week. – MaQleod Mar 7 '11 at 3:37

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