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iblock is an inetd program adding the client IP to a Packet Filter table. It is meant to be used to block scanner connecting on unused ports.
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README.md

iblock

iblock is an inetd program adding the client IP to a Packet Filter table.

It is meant to be used to block scanner connecting on unused ports.

How to use

Start inetd service with this in /etc/inetd.conf:

666 stream tcp nowait root /usr/local/bin/iblock iblock

Use this in /etc/pf.conf, choose which ports will trigger the ban from the variable:

# services triggering a block
blocking_tcp="{ 21 23 53 111 135 137:139 445 1433 25565 5432 3389 3306 27019 }"

table <blocked> persist

pass in quick on egress proto tcp to port $blocking_tcp rdr-to 127.0.0.1 port 666
block in quick from <blocked> label iblock

Done! You can see IP banned using pfctl -t blocked -T show and iBlock will log blocking too.

In the example I added a label to the block rule, you can use pfctl -s labels to view statistics from this rule, see documentation for column meaning.

TODO

  • make install doing something
  • A proper man page
  • Support IPv6
  • make it work with doas
  • pf table as a parameter