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Firewall fails to block an established UDP connection...

GreatByte
Hello Guys,

I am have a weird situation here. I have a PC communicating with a server, both connected to my Sophos Firewall (Firmware: 9.100-16 - not an appliance).

I have a Rule that allows this connection, and it works. Without that Rule, the connection cannot be established. So far so good.
Once established, however, the communication continues even if I disable that rule, or add a rule above it to block that connection. [:S]
It just keeps on working and there doesnt seem to be a way to block it if I wanted to...

I tried it using a PC connected via the Internet and I can even disable the DNat Rule and the connection still continues. Only new connections are being blocked. Is this an expected behavior? Doesnt seem right to me.

Greatbyte


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    bblank:  In theory, tcp connections should and likely will re-establish themselves.  In the real world though things can be very different.  I would advise being careful about deploying this to everyone right away, perhaps start with a smaller subset of users who opt in to trying this new tactic.  

    Conntrack supports deleting specific connections, I propose you write a cronjob that dumps connections for that specific subset of  users to measure the impact before deploying this widely.
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  • 0
    bblank:  In theory, tcp connections should and likely will re-establish themselves.  In the real world though things can be very different.  I would advise being careful about deploying this to everyone right away, perhaps start with a smaller subset of users who opt in to trying this new tactic.  

    Conntrack supports deleting specific connections, I propose you write a cronjob that dumps connections for that specific subset of  users to measure the impact before deploying this widely.
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