Re: New DoS attack

[huuskone () CC HELSINKI FI (Taneli Huuskonen)]

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Dave Booth <dave.booth () MEDTRONIC COM> wrote:

[...]
> Game client makes tcp connection to server and requests to join the
> game.
> Server responds (as part of the same tcp session) with a unique token,
> remembers it and the clients IP then signs off.
> Client initiates normal UDP game connection including the token in
> every datagram.
> Server silently ignores all incoming datagrams where there isnt a valid
> token that matches up with the IP address the datagram claims to come
> from.

This thread was originally about the use of game servers as traffic
amplifiers for smurf-type DoS attacks.  The problem is that a game
server can be tricked into sending relatively large amounts of data in
response to a blindly spoofed request to join the game, thereby flooding
the spoofed address.

It seems to me that your suggested protocol would indeed solve the
problem, but I think it's overkill.  The same result is achieved by
having the server reply to the initial contact attempt with a packet
containing essentially nothing but the token.  After that, continue like
you propose.  Much simpler and cleaner, IMHO.

Taneli Huuskonen

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