Re: [fw-wiz] Help w/ Port 137 Traffic

From: Mikael Olsson (mikael.olssonat_private)
Date: Sun Oct 13 2002 - 05:57:10 PDT

  • Next message: Paul D. Robertson: "Re: [fw-wiz] Help w/ Port 137 Traffic"

    "Paul D. Robertson" wrote:
    > 
    > http://www.ciac.org/ciac/W32_BugBear_info.html
    > [...]
    > I suspect the worm does a lookup prior to an infection
    
    This is _possible_. If the worm prefers logging on with 
    "computername\username" rather than just "username", it would have to 
    get the netbios host name first. I don't see _why_ it'd be doing it;
    I'm just saying it _could_.
    
    > , but I really don't
    > know- I don't run Windows, so I haven't played with doing NetBIOS stuff
    > and don't know what the normal programming sequence is for enumerating
    > shares, and as we don't let customers expose NetBIOS ports at all, this
    > was never high on my list of things to worry about.
    
    I've personally never seen share enumeration being done over port 137.
    I have only seen it done over 139, and I guess it can be done over 
    port 445 as well.
    
    "nbtstat -a computername" however returns a list of "names" associated
    with the box. This includes: the computer name, the domain/wg name,
    and the name of the currently logged on user.  How this can help a worm,
    i don't know.
    
    
    Anyway, what I do know is that you don't access shares (infect things) 
    over port 137.  This happens over 139/445.
    
    My guess would be that ciac got it (the _important_ facts) wrong. 
    I do know for a fact that their recommendations are a bit off; they only 
    recommend to firewall ports 137--139, which is a bit narrow for my taste; 
    it exposes the portmapper (135) as well as port 445.
    
    /Mike, off to write a note to ciac about fixing their documentation
    
    -- 
    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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