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IP Address's


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5 replies to this topic

#1 ironjack

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Posted 24 August 2014 - 06:43 PM

I am still using 2 old computers running XP.I am going to purchase new computers soon.My question is,"If my old machines have been compromised and a hacker has access to them,will purchasing new do any good?" I am concerned about my IP address's.Are they the same if I remove the old and hook up the new at the same physical location?

 

 



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#2 Kilroy

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Posted 24 August 2014 - 09:28 PM

There is a bit to understand here.  First, you most likely have a router since you are using two machines.  If your router has been compromised your issues may continue.  Your router is more likely to be compromised if you have left the default administrative passwords in place.

 

There are two IP addresses, your Public IP address (this can be found by going to What Is My IP.com) and your local area network address (LAN)(most likely 192.168.x.x).  The LAN address will most likely change, but since the 192.168.x.x IP addresses cannot be routed on the internet it doesn't matter if someone knows your LAN IP address.  The Public IP address is the address that you get from your ISP and it will most likely remain the same.  If you are using a router that has not been compromised this shouldn't be an issue since all non-requested information will be dropped by the router since it does not know where to send the information.  If you suspect your router has been compromised you should probably look to updating the firmware, reconfiguring, and changing the default administrative password.



#3 scotty_ncc1701

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Posted 25 August 2014 - 10:02 AM

The Public IP address is the address that you get from your ISP and it will most likely remain the same.

"The Public IP address is the address that you get from your ISP and it will most likely remain the same" is misleading, AT LEAST IN PART.  Specifically, if a hard reset of the modem is done, the public IP address will change.  Also, if the modem has a "reboot" button as show below will also change the public IP address, after the reboot (of the modem) occurs.  The "reboot" button is the same has a hard reset.

START:
34gsnlg.jpg

AFTER HARD RESET (RECESSED RED BUTTON):
a5cbqh.jpg

AFTER SOFT RESET ("REBOOT" BUTTON)
n569l3.jpg

On renewal of the IP address, it may not change, thus my comment of "You are mistaken on your comment of "The Public IP address is the address that you get from your ISP and it will most likely remain the same", AT LEAST IN PART".  However, in all cases, when I paid attention, mine did change.

Have a great day!
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#4 Joe C

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Posted 25 August 2014 - 10:33 AM

If you want an ip address that does not change, you have to pay your isp extra for a static ip address, otherwise like Scotty stated, it can change anytime you reboot your modem or disconnect from your isp for a lenth of time



#5 ironjack

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Posted 25 August 2014 - 07:18 PM

Thanks to Kilroy,Scotty_Ncc1701,and JoeC.

I 'preciate ya' fellas!  :smash:



#6 Didier Stevens

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Posted 26 August 2014 - 04:50 AM

There are many possibilities.

 

A fixed IP address is when you configure your device with an explicit IP address (e.g. you type the IP address in the configuration), a dynamic IP address is when your device uses DHCP to obtain an IP address.

 

With DHCP, your IP address might change when you get a new lease. But this depends on several factors.

For example, it's possible to always get the same IP address even with DHCP: that is done with a reservation on the DHCP server. The MAC address of your device is entered into the DHCP server configuration, together with an IP address.

When your device requests an IP address via DHCP, the DHCP server will always give you the same IP address (the one that is reserved for your device).

 

If there is no reservation, the DHCP server will assign you a free IP address from its pool.

 

Why do you sometimes get the same IP address and sometimes not? This depends on different factors.

 

If your former IP address is in use by another device, you can not lease it.

 

A full DHCP communication is: Discovery, Offer, Request, Acknowledge.

But there is also a shorter one: Request, Acknowledge.

With a request, the device can request the same IP address.

When a device is booted, it always does the full DHCP communication. That's why it's more likely to get a different IP address.


Didier Stevens
http://blog.DidierStevens.com
http://DidierStevensLabs.com

SANS ISC Senior Handler
Microsoft MVP 2011-2016 Consumer Security, Windows Insider MVP 2016-2019
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