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Petry pretty much nails it. Basically, your setup permits traffic to a http/https/ftp port, but does not accept traffic coming from that port -- so your query goes out, but the response gets dropped. Like most modern firewalls (defined as "after 1995 or thereabouts") the linux firewall tracks connections and allows for state-based filtering. The line ...


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You're not letting any related connection in... Quick way to fix it...: #iptables -I INPUT -m state --state RELATED,ESTABLISHED -j ACCEPT P.S: sorry for posting in a rush, i'm in my way to work. I'll come back with details 😉 Now, the details... Every time you want to connect over TCP/IP, there's a "three way handshake". Let's say you want to connect to ...


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Assuming Barracuda have correct rDNS records, add an ACL at helo time and only accept connections which verify and are from their domain. The following should be a good starting point. The Exim documentation provides additional details. These rules could be added at connect time, but is likely to result in legitimate servers retrying. However, they ...


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You can use TCP wrappers for doing this, /etc/host.allow or /ect/host.deny you can mention your network pool in this file with the users.


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Wikipedia has a great diagram to show the processing order. For more details you can also look at the iptables documentation, specifically the traversing of tables and chains chapter. Which also includes a flow diagram. The order changes dependent on how netfilter is being used (as a bridge or network filter and whether it has interaction with the ...


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Try this, iptables -A OUTPUT -o ethX -m owner --uid-owner {USERNAME} -j DROP Where, --uid-owner { USERNAME } : Matches if the packet was created by a process with the given effective USERNAME. -A : Append rule to given table/chain -I : Insert rule to head of table/chain For example, my oracle user id is 1000 so I will append following rule: ...


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I think you're looking for authpf. http://www.openbsd.org/faq/pf/authpf.html Authpf(8) is a user shell for authenticating gateways. An authenticating gateway is just like a regular network gateway (a.k.a. a router) except that users must first authenticate themselves to the gateway before it will allow traffic to pass through it. When a user's shell is ...


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Firewalls generally look at network packets. They can see where packets come from, but unless it's somehow revealed by packet introspection, they don't know who is responsible for those packets. You could start with everything locked down for everyone, and then add in authenticated access as needed. e.g. via an authenticated proxy which all external web ...


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You can use an online tool such as www.firewallruletest.com to see if external hosts can establish tcp connections.


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I can't give you a general plan and then hopefully someone else can fill in the details. It looks like you're going to need to do the following: Create a chroot Somehow allow only one interface to it. Then look at packet queuing for that interface or write your pf rules on that interface. Honestly, I think it'd be easier with FreeBSD jails, but your ...


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If you are concerned about system integrity, then selinux or grsecurity (or the various similar security packages) are very powerful. Unfortunately, mastering their policies is far from trivial. (Any decent distro that includes SELinux will have predefined policies for all kinds of things, though.) Grsecurity policies are easier to create but still require ...


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-A OUTPUT -o eth0 -p icmp --icmp-type ping -j ACCEPT -A OUTPUT -o eth0 -j DROP -A FORWARD -i eth1 -o eth0 -j ACCEPT -A FORWARD -i eth0 -o eth1 -m state --state ESTABLISHED,RELATED -j ACCEPT -A FORWARD -i eth2 -o eth0 -p tcp --dport 80 -j ACCEPT -A FORWARD -i eth2 -o eth0 -j DROP -A FORWARD -i eth0 -o eth2 -m state --state ESTABLISHED,RELATED -j ACCEPT ...



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