Re: Flaw caused by default rulesets in many desktop firewalls under windows

From: Christian decoder Holler (christian_hollerat_private)
Date: Sat May 11 2002 - 07:43:23 PDT

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    Only as an addition:
    
    Tiny personal firewall for example allows ANY communication 
    on port 53 UDP outbound, it does not even check if that is 
    really a DNS request. This is a big security hole that 
    should be fixed immediatly.
    
    Note: I also saw that some default settings of ZoneAlarm 
    have DNS requests enabled or they enable them while using 
    ZA. I have not tested my trojan with ZA yet, so I dont know 
    if ZA checks if those requests are valid DNS requests, but 
    there is a possibility that the hole also affects this 
    firewall. If anyone finds out if other firewalls are 
    vulnerable, I would be happy to hear about that.
    To test that, simply write a program that connects to 
    another computer in your network on UDP 53 where you listen 
    with netcat for example and send a string. If the firewall 
    doesnt alert this connection, then it is vulnerable.
    
    cu
    
    Chris (decoder)
    



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