Re: [fw-wiz] CERT vulnerability note VU# 539363

From: Mikael Olsson (mikael.olssonat_private)
Date: Wed Oct 16 2002 - 05:43:33 PDT

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    Stephen Gill wrote:
    > 
    > Thought I'd pass this along.
    > 
    > http://www.kb.cert.org/vuls/id/539363
    
    Although this is something that people need to keep in mind when 
    picking / designing a firewall, I'd argue that anything north of
    a stateless packet filter is going to be vulnerable to these sort
    of attacks.  
    
    If you keep state, you will be vulnerable to state table overflows. 
    Period.  The only real question is: how much work does the attacker 
    need to put in before it becomes painful for the networks that the 
    firewall is protecting?  Is being able to resist a  1 Mbps stream 
    (~4500 pps) "Not vulnerable"?  Is being able resist a 34 Mbps stream
    (~150 kpps) "Not vulnerable"?  Or should every single firewall
    vendor report in and say "Vulnerable", and describe what the limit is?
    
    
    And, yes, ALG-only firewalls can also be overloaded. It's just a 
    different type of 'state'.
    
    -- 
    Mikael Olsson, Clavister AB
    Storgatan 12, Box 393, SE-891 28 ÖRNSKÖLDSVIK, Sweden
    Phone: +46 (0)660 29 92 00   Mobile: +46 (0)70 26 222 05
    Fax: +46 (0)660 122 50       WWW: http://www.clavister.com
    
    "Senex semper diu dormit"
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