Re: Routing and Remote Access NAT - I need to modify TTL

Tech-Archive recommends: Repair Windows Errors & Optimize Windows Performance

"Ace Fekay [Microsoft Certified Trainer]" <aceman@xxxxxxxxxxxxxxxxxxxxxxx>
wrote in message news:eIC2MSY4JHA.1716@xxxxxxxxxxxxxxxxxxxxxxx
"George Valkov" <a@xxxxx> wrote in message
news:uwBJ8yX4JHA.6004@xxxxxxxxxxxxxxxxxxxxxxx
About 3 years ago the students were building their own free LANs
interconnecting computers on one or more blocks (hostel). Everyone who
joined, brought his/her own cabling and paid once just to cover the money
for a port of a switch. The bad thing was that organisation was poor,
cables
were passing through windows and terraces and there were long cables from
one block to another. Some terraces did look like huge spider webs :-) WWW
;-)
A few ISPs were connected to the same LANs. Back then, the Internet was
slow, there were outages, viruses... It's was a wild and free network.

Then came megalan, as far as I heard they made some deal with the
university
and became monopolist among the students town. Broke all the free
networks.
Now there are no worms and the only one APR poisoning the network is the
ISP
it self - they said to filter File and Printer Sharing and prevent worms
from spreading.

In fact the main reason for the ARP poisoning is to monitor all of the
traffic and determine if some of the clients wants to share the connection
or perform something that the ISP doesn't like. If a packet from
MAC-ADDRESS_A but IP_B arrives at the gateway, they consider that A is
trying to steal the IP of B, so they block access to the MAC-ADDRESS_A. I
wonder if they know that since custom MAC addresses can be assigned any
bad
guy can cause denial of service on other clients by using their MAC with a
different IP, causing the security system to block MAC-ADDRESS_A. A client
can also set two computers to make a lot of traffic to each other, and
because of the ARP poisoning, that appears to be an innocent way to flood
the gateway. But they don't seem to understand how dangerous their
security
measurements can be.

Good night, Ace!


George Valkov

| Ahh, very interesting, indeed! This all makes sense now. So this was a way
| for the ISP to control this mess and not allow this haphazard sharing one
| connection for the whole city block. They still do that with cable TV in
some
| areas, I hear, or at least stealing or sharing a neighbor's cable TV
connection.
| I guess that will never stop, but the digital boxes make it difficult to
get premium
| channels without the box.

I've heard that some sattelite digital boxes like DreamBox (which runs on
Linux) can share their card over the Internet, when internet connection is
available (RJ45 LAN cable). Then the other DreamBox can use that shared card
to decrypt the premium channels. :-) So the cable operators started to offer
receivers very cheep. The boxes have custom firmware and will lock down if
not used on with that provider for 3 days. When the box plays a channel from
the provider, the timer gets reset and the box unlocked.


I can also see how based on your explanation, spoofing a MAC can cause
| problems with others. I guess as long as all users do not know other
users'
| MACs, they will not cause any type of DOS on someone else's machine.

| Cheers!

| Ace


You are right! That really makes sence! Finding other users' MACs is a very
hard task, I was able to accidently find 3 MACs a few months ago. Then I
learned that the static APR assignment must be on the both sides, otherwise
the GW still get's in the middle, but in one direction only. Packets with
others MACs almost never reach my computer. Even those from my room-mate's
PC that is connected to the same switch. Unless maby if I change mine's MAC
and IP to those of the GW and start heavy poisoning like them too. ;-)


George Valkov


.

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