Flawed workaround in MS02-027 -- gopher can run on _any_ port, not just 70

From: Mikael Olsson (mikael.olssonat_private)
Date: Thu Jun 13 2002 - 09:57:07 PDT

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    Just a quick heads-up:
    
    MS02-027 cites blocking port 70 as an effective protection against
    exploitation of the Gopher buffer overrun in IE / ISA server / MS proxy:
    
    "Most notably, customers who block access to the Gopher protocol (TCP 
     port 70) at the perimeter firewall would be protected against attempts 
     to exploit this vulnerability across the Internet."
    
    
    This is untrue. Gopher servers can run on any port, e.g.
    "gopher://evilhacker.net:1234", or why not ":80", so don't trust 
    blocking port 70 at all. Use the other workarounds instead.
    
    (In fact, in the case of *nix servers, it's even easier for an attacker 
    to run the fake gopher server on a high port; this way, he won't even 
    need root priviliges.)
    
    
    Take care,
    /Mikael Olsson
    
    -- 
    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
    



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