# 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 ## Add a dedicated user ``` useradd -s /sbin/nologin _iblock ``` ## Configure doas Add in `/etc/doas.conf`: ``` permit nopass _iblock cmd /sbin/pfctl ``` ## Configure inetd Start inetd service with this in `/etc/inetd.conf`: ``` 666 stream tcp nowait _iblock /usr/local/bin/iblock iblock 666 stream tcp6 nowait _iblock /usr/local/bin/iblock iblock ``` You can change the PF table by adding it as a parameter like this: In this example, the parameter `blocklist` will add IPs to the `blocklist` PF table. ``` 666 stream tcp nowait _iblock /usr/local/bin/iblock iblock blocklist 666 stream tcp6 nowait _iblock /usr/local/bin/iblock iblock blocklist ``` ## Configure packet filter 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 persist block in quick from label iblock pass in quick on egress inet proto tcp to port $blocking_tcp rdr-to 127.0.0.1 port 666 pass in quick on egress inet6 proto tcp to port $blocking_tcp rdr-to ::1 port 666 ``` Don't forget to reload the rules with `pfctl -f /etc/pf.conf`. # Get some statistics Done! You can see IP banned using `pfctl -t blocked -T show` and iBlock will send blocked addresses to syslog. 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](https://man.openbsd.org/pfctl#s~8). # TODO - make install doing something - A proper man page