Re[2]: Why TCP is more secure than UDP?

Hello Buz,

Thank you for your details.
What you describe looks to me like some land or smurf-attack.
Let me go on...
i) using the conf. you describe, if i understand you well, even 1
legitime ECHO will start some pending of packets.
ii) as you describe it is for me a M-I-T-M attack where you basicaly
spoof an IP

The point that you use TCP ur UDP doesnt really matter, because as i
mentioned, the only thing which makes TCP harder to break is the
pre-established connection with the seq-number.
Taking this in consideration, if Moe sniffs the traffic he can hijack
the TCP-Session or try to guess the seq-nr.
But as i mentioned, we dont spoof here TCP or UDP, we basicaly spoof
an IP and start an man in the middle (M-I-T-M) attack on the
respective protocol.

Best regards,
Adam Pal

Considering your scenario, if the router is configured
not to accept inbound traffic with rfc-1918 source-addresses everything is ok.
From that point of view it can be also a weakness of the router conf.
more than a weakness of the protocol? :)

Wednesday, July 11, 2007, 9:18:42 PM, you wrote:

<==============Original message text===============
BD> I'll try and illustrate a security difference. Lets say I have a
BD> service called "Echo" that runs on both udp port 7 and tcp port 7 on
BD> two machines on my lan (192168.1.1 or "Larry" and or
BD> "Curly".) Suppose this service just echoes back any packet I send it.
BD> Suppose my tricky friend "Moe" is across the internet at (Oh
BD> yeah - and let's also suppose these are not rfc 1918 addresses.) Moe's
BD> router and ISP are configured kinda loosely and don't really care
BD> about source addresses, just destination.

BD> If Moe uses a UDP packet with source and destination
BD>, his first packet could (if My router configs are a
BD> little loose) get that packet to Larry, the content of that packet
BD> "SLAP" will get echoed to Curly who will then SLAP Larry who will
BD> then SLAP Curly ad inifinitum. Burning network and CPU until noticed.
BD> (works well actually with port 19 and Chargen as one of the ports and
BD> 7 as the other.)

BD> If Moe uses a tcp packet with source and a destination
BD> of His packet will get to Larry and Larry will try and
BD> handshake with Curly who won't have any idea of what's going on and
BD> stop the transaction.

BD> It's easy for Moe to "spoof" either udp or tcp but the udp packet is
BD> more fun for Moe.

BD> Luck,
BD> Buz

BD> On 7/10/07, pal_adam@xxxxxxx <pal_adam@xxxxxxx> wrote:

I dont understand what you mean by spoofing, since wherever you
use UDP or TCP the underlying layer still remains IP so when you
spoof a source you spoof an IP source.
If you talk about a man-in-the-middle attack then taking a
closer look at both protocols will show that UDP doesnt establish
any connection before starting the communication.
Using TCP you`ll need to ACK incomming data using a
pre-established sequence number which makes the attack on TCP
harder but not impossible.


Adam Pal

-------- Original-Nachricht --------
Datum: 10 Jul 2007 02:11:12 -0000
Von: paavan.shah@xxxxxxxxx
An: security-basics@xxxxxxxxxxxxxxxxx
Betreff: Why TCP is more secure than UDP?

It is said that UDP is considered more vulnerable to spoofing than TCP?

Can anyone point me to any document/link which describes TCP is more
secure than UDP

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