Yesterday I installed Cent OS 6 and had to flush the default IPtables rules (IPtables -F) in order to access a web app via my browser.

Having very little experience with Linux/Network security this got me thinking about how open to attack I am with the rules flushed.

I know/assume/hope my router has a firewall which protects me from attackers on the wider PDN (i.e. internet).

But I am wondering am I now wide open to attack if someone plugs directly into my LAN?

Also, even with an effective IPtables rule strategy can I still succumb to attack, does the firewall perform all blocks/permits/redirects when packets arrive at the NIC or do they proceed past the NIC onto the CPU before the being accessed against the IPtables rules?

  • DDoS can still cripples the network, but that is something beyond the roles of firewall. Within the LAN, that is everything about policy, or make use of VLAN to isolate possible infectious attack from unsafe segment of the network. Using a firewall to isolate LAN is not unheard of, but it is kind of costly and tedious.
    – mootmoot
    Aug 9 '18 at 11:38
  • @mootmoot Ok thank you. Yes, I am aware of DDoS. Unsure how to defend against it apart form setting some kind of maximum number of permitted requests in a specific time interval rule. But thanks for the information about the VLAN. I assume you mean the VLAN acts as some kind of DMZ between the LAN and external PDN?
    – MarkMark
    Aug 9 '18 at 12:54
  • A switch with VLAN suppport (802.1Q)let you create separate network segment minus complexity of a network bridge. You can use to create a DMZ or even segment the LAN.
    – mootmoot
    Aug 9 '18 at 13:40

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