Re: Simple DOS attack on FW-1

From: James Burns (jburnsat_private)
Date: Sat Jul 31 1999 - 18:13:55 PDT

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     > Sure this is the case if you have a rule set that has something like.
    Let
    > in a packet that is bound to some address range.
    > If I have a rule set that is host based, allowing only a few specific IP
    > address's in the DoS attack is limited?
    >
    > Increasing the size of the connections allowed in the table may only
    reduce
    > the possibility of the attack.  Why not increase the number such that it
    is
    > greater than what your bandwidth can handle (advocated by firewall people
    > here).
    >
    > r1ccard0
    >
    > Richard Scott
    > (I.S.) E-Commerce Team
    > * Best Buy World Headquarters
    > 7075 Flying Cloud Drive
    > Eden Prairie, MN 55344 USA
    >
    > This '|' is not a pipe
    
    Even if you have a few specific IPs, if they can be found, they can be
    spoofed since there is no sequence number checking. I guess your security
    then depends on how hard the trusted IPs are to guess. (Probably a bad idea)
    In regards to increasing the connection table to a number greater the your
    bandwidth can handle, well, first I'm not sure that that's a meaningful
    statement. The maximum number of connections for a given bandwidth depends
    on what's going on in those connections. However, the faked connections are
    only 1 packet and I don't think that you could expand the table enough to
    hold even 56k bps of faked packets.
    
    -James
    



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