Their are many forms and uses for IP addresses, I will go over a few for you.
External (WAN IP): Used for a other computers in the world to send you data to your computer, how else are they going to send data to you?
: Your ISP has a fixed IP for you and it does not change when you reset the modem or after a certain period of time, this is common
for DSL and is populor as you can host.
: Each time your modem reconnects and to the ISP you obtain an new IP, in some cases the ISP may force a new IP on you ever 24
hours. Cable and mobile internet is almost always dynamic.
Its worth noting most ISP's record the IP's the allocate to users and any given time, it is not any safer and does not stop authority tracking
You can disguise this IP (not hide) by using software such as TOR, VPN's and the use of proxy's which redirect your traffic through their
internet...(you appear as their IP)
Like always your security always depends on the security of the other links, if your proxy is compromised then you may be worse off...use encryption
where possible and known secure links.
Internal IP (LAN)
An Internal IP used to identify and send data to each networked device in the network, without it the router wouldn't know where to send the
An internal IP may look like 10.0.0.1
To obtain a new IP (given your router is on DHCP) you only need to plug the network cable in and out.
This will not prevent a agency from tracking you, agency's almost always go after your WAN ip.
["The easiest way to obtain a new ip address is by getting a new Ethernet card."]
No, this is untrue.
A new ethernet card will do nothing for your IP, it may give you a new "MAC address" however this can easily be spoofed by software and serves no real
use other then identifying computers on an internal network and the use in network switches.
If your worried use a cheap ebay ethernet card as the mac address will most likely be similar across a wide range of cards and not unique to that
Hope this helps
edit on 13-4-2012 by phantom150 because: (no reason given)