Hi I am sorry to hear you just woke from your coma. It is now 2007 not 1995.
On 10/25/07, Oliver <[EMAIL PROTECTED]> wrote: > > > Hello, > > I have been searching all over the place to find an answer to this question, > but Google has made me feel unlucky these last few days. I hope I could find > more expertise here. The burning question I have been pondering over is - > could TCP connections be hijacked both ways? I know there are tools ( e.g. > Hunt) that sniffs traffic and could arbitrarily reset a connection by > spoofing the IP and MAC address. But could there be more than just that? Is > it theoretically possible to not reset the connection with the server or the > client, but play the man-in-the-middle attack? > > An example network scenario of this that I could come up with is that the > hacker is within the same network as the victim (client), who is connected > to a server through a persistent TCP connection. Now the hacker could > pretend to be the server and send a TCP message (not reset/fin) to the > client and change the seq/ack numbers on the client side, and the hacker > could pretend to be the client and send a TCP message (not reset/fin) to the > server and change the seq/ack there. Thus, the seq/ack numbers are > completely out of sync for the client and server and thus would not > recognize each others messages. At this point, the hacker could relay ( i.e. > be man-in-the-middle) the messages from the client to the server and vice > versa, using the seq/ack numbers that they would accept. While this seems > pretty pointless so far, the hacker could inject messages at will to either > side of the connection, and still make the server and client believe that > they are in sync with each other ( i.e. this would not work if the hacker > does not relay the messages with the seq/ack numbers the server and client > would accept). That means the hacker goes undetected and could do whatever > he chooses, as he has "hijacked" the connection. > > Is this possible? Assuming there is no hardware limitation (e.g. > router/switch blocking MAC/IP addresses from certain port). Would the TCP > protocol definition and implementation in Windows and *nixes these days > would interpret this behaviour correctly (correctly for the hacker, > incorrectly for themselves)? I imagine it would be quite a bit of work > proving this theory and perhaps some of you could enlighten me or dismiss > this concept. > > Regards, > Oliver > > _______________________________________________ > Full-Disclosure - We believe in it. > Charter: > http://lists.grok.org.uk/full-disclosure-charter.html > Hosted and sponsored by Secunia - http://secunia.com/ > _______________________________________________ Full-Disclosure - We believe in it. Charter: http://lists.grok.org.uk/full-disclosure-charter.html Hosted and sponsored by Secunia - http://secunia.com/
