Given that most Zeroshell routers will be exposed directly to the Internet (the red zone), it would be nice to have fail2ban installed.
I’d be willing to work on configuring some of the jails and posting the configurations.
I know that the intended design of zeroshell is not to expose anything to the Internet side by not having open services and ports, instead using the VPN interface. However, this does not prevent attacks from the internal network interfaces.
Anyway, fail2ban is lightweight, simple to use and would be a nice addition to zeroshell.