Wikipedia:Reference desk/Archives/Computing/2017 February 22

= February 22 =

From Help desk: WP links
I have a query over at the Help desk that I initially thought was Wikipedia related, but might be better asked here (no satisfactory reply yet). Rather than duplicate, here is the link: Help_desk --tyia, 2606:A000:4C0C:E200:55A:7C25:5B38:2DC5 (talk) 03:56, 22 February 2017 (UTC)
 * Your question is indeed firefox-related. Answered you on the other page. :) Jahoe (talk) 14:06, 22 February 2017 (UTC)
 * As Jahoe said on the other page, this isn't cookie (or cache) related, but history related. I use Firefox myself (I have regular with an old copy of firebug installed as well as the developer's edition), and I can clear my 'visited links' from deleting the page the link is to from my history, then refreshing the page I'm viewing. ᛗᛁᛟᛚᚾᛁᚱPants   Tell me all about it.  14:38, 22 February 2017 (UTC)
 * In my confusion I answered on the other page. Mr. Pants is of course right in continuing here, because the question is not wikipedia related. Jahoe (talk) 15:41, 22 February 2017 (UTC)

Changing sat nav information
Does anyone now how the information in a sat nav can be changed? Not by the owner/user but by a third party. This recently happened to me, my HOME information set into my sat nav should have directed me a certain way but directed me the opposite way. The home location had been set in the sat nav from new, I had not changed it and yet when coming along a road, it directed me to turn left instead of right as it usually does. I made some texts about this odd occurrence and within 10 minutes or so it had reverted to its usual directions.Rod Fathers (talk) 17:43, 22 February 2017 (UTC) (copied from Talk:Spoofing attack by Alcherin)
 * Well, the home information is generally stored on the device, and not part of the network. So most likely, you had a brief communication issue between your device and the satellites, which caused it to think it was at a different location than it actually was.
 * If, however, you checked the home address during this time and found that it was a different address to the one you inputted, then it was most likely a bug that caused some address stored in memory to get swapped out with your home address.
 * Finally, hacking of GPS systems generally only occurs when those systems are embedded into other devices, due to the difficulty of spoofing a satellite signal, vs the (very) relative ease of connecting to your phone via bluetooth, wifi or 4G and then forcing the OS to change the data coming from the satellites before it gets used by the navigation application. You can check out this article for some information about that. ᛗᛁᛟᛚᚾᛁᚱPants   Tell me all about it.  19:35, 22 February 2017 (UTC)


 * Was your home location changed, or did it just use a different route? LongHairedFop (talk) 19:48, 22 February 2017 (UTC)


 * Before answering, you should read the person's talk page. I seriously doubt it will be possible to convince him that there is any possibility that it was just a glitch. It must be a malicious hack performed by some unknown shadow agency. 209.149.113.5 (talk) 19:58, 22 February 2017 (UTC)
 * Regardless, this forum exists to provide answers. As long as the editor asking questions isn't being disruptive, there is no harm in providing accurate answers. ᛗᛁᛟᛚᚾᛁᚱPants   Tell me all about it.  20:09, 22 February 2017 (UTC)


 * While GPS spoofing is theoretically possible, it's very unlikely that this would be done to target an individual driver, and it wouldn't cause the symptoms you describe. (It would convince your GPS that your current location was elsewhere, Dangerous on the open seas, but you'd figure it out pretty quick when the roads you saw with your eyes didn't match the roads on the map.)
 * More likely you were navigating to the wrong address. Either because you typed in a common address and it guessed wrong, (For example, if you typed in "123 Main St. Springfield", it would probably take you to the closest town of that name, not necessarily the one where you happen to live.), you simply typed it in wrong,  or you were relying on a preset address that somehow got reset to factory defaults. (Perhaps because of a firmware reset? Or dead battery on an older unit with volatile storage.)
 * Hope this helps. ApLundell (talk) 21:00, 22 February 2017 (UTC)
 * Oh, I forgot. Some devices (including Google Maps on your phone) take current traffic conditions into account when they plan your route. (See Google_Traffic.)
 * This means that if there's a traffic jam along your usual route, it will direct you along an alternate route. This sounds like what happened to you.  If you sat around and waited until the traffic jam cleared up, you would be directed along your normal route as usual. ApLundell (talk) 21:03, 22 February 2017 (UTC)

Can someone make a router re-send packages?
If someone is not connected to a router, could he spoof a MAC nummer and make the router resend packages? That would be a kind of DoS attack, but on a private network. --Llaanngg (talk) 20:09, 22 February 2017 (UTC)
 * Surely you mean MAC number and packets, right? In that case, that's not how link-layer routing works. The notion of resending packets is done at the application layer (i.e. transmission control protocol).--Jasper Deng (talk) 20:19, 22 February 2017 (UTC)
 * If someone is not connected to a router, it will be very difficult to make that router do anything. (I would suggest yelling at it as the best way to go. Routers are very timid things and are easily intimidated.) For someone who is not directly connected to the router, it all depends on what they can force a machine directly connected to it to do, and what the router allows that machine to tell it to do. To be clear, Jasper is right that resending packets is not done at the network layer. Check out OSI model for an article about what is handled at what layer. ᛗᛁᛟᛚᚾᛁᚱPants   Tell me all about it.  20:26, 22 February 2017 (UTC)
 * I wonder whether someone physically close to the router and to the client would be able to spoof a NACK signal (and make it look as if it's coming from the client), and so make the router retransmit the packet. Would a timid router think this is the legit client telling him to send the packet again?--Llaanngg (talk) 22:42, 22 February 2017 (UTC)
 * This is one reason for randomization of sequence numbers.--Jasper Deng (talk) 00:38, 23 February 2017 (UTC)
 * And what if I capture a packet send by the client and send it again and again? What would the router do? Llaanngg (talk) 00:54, 23 February 2017 (UTC)
 * There's a name for this: man-in-the-middle attack. Also, you might want to read up on TCP congestion control, and note that the router will be oblivious to the whole thing as long as it is not itself the opposite endpoint of the TCP socket. Also, duplicate packets are to be simply dropped by the endpoint (they can be identified by having the same sequence number).
 * I sense that you don't completely understand how TCP works, so reading up on that would be a good start.--Jasper Deng (talk) 01:22, 23 February 2017 (UTC)
 * Is it me or is there some confusion here? The OP talks about MAC-address spoofing and a private network, so I guess he talking ethernet frames, rather than TCP packets.
 * Because MAC addresses are only valid within the local segment, the spoofed address would not be seen by routers outside the local network.
 * Not sure if this answers the question. Jahoe (talk) 15:04, 23 February 2017 (UTC)
 * Perhaps more clear: routers unpack the data (an IP packet) from their ethernet frame, and repack it for the next hop. Gone is your spoofed MAC address, because it's part of the frame header. The first router to do so would probably be your own internet modem/router. MAC addresses are not visible across hops or across the internet. Jahoe (talk) 15:33, 23 February 2017 (UTC)