For the purposes of this exercise, we assume a gateway machine, running a simple firewall, which we want to use to drop various packets on the floor - such as those from machines particiapting in a distributed brute for ssh attack, for instance. We assume there are several scripts managing the blocked list. For best effect, your gateway box should be mounting a few directories via nfs from another machine.
- Ensure that packets between the gateway box and the file server need to traverse the blocked list first.
- Don't lock properly when adding new IPs to the firewall. This ensures that, under load, you can add large numbers of duplicate entries to the list.
- Have every packet traverse the blocked list twice.
 Which means exactly what I think it means.