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    SubjectRe: 2.2.12 tcp flaw
    On Mon, 4 Oct 1999, meridian wrote:

    > I read SOMEWHERE in the last few days that there is a flaw in all
    > 2.2.x and 2.3.x kernel code tcp stack including 2.2.12 allowing something
    > like session hijacking or a similar attack yet have seen no discussion or
    > patches for it here. Have I been misinformed or is it just quietly being
    > worked on? Thanks
    > meridian

    This is just some more diatribe. Once a connection is established, all
    Ethernet TCP/IP implimentations (even W$) communicate (see ARP)
    hardware-to-hardware. A hijacker would have to take your ethernet
    controller out of your box and used it to hijack your communications.

    But.... many ethernet controllers, in violation of their original
    license to use an assigned MAC address, allow the MAC address to be
    set in software. This means that, in principle, it is possible for
    any machine on your LAN to completely and transparently pretend that
    it is you. There is no way that any TCP/IP stack anywhere can defend
    against this because the emulation is perfect.

    Look at recent Ethernet driver code. You will note that the MAC address
    is simply stored somewhere and software has to take it and put it
    into the Ethernet header. This is not the problem however, recent
    controllers allow software to set the MAC address it will receive.

    This means that you can send/receive with a MAC address of anything you
    want including the Payroll Computer that has already established a
    connection and is writing checks.

    Dick Johnson
    Penguin : Linux version 2.3.13 on an i686 machine (400.59 BogoMips).
    Warning : It's hard to remain at the trailing edge of technology.

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