If you're looking for a worthwhile project, here's something that could benefit most security practitioners. The application "fail2ban" has been extremely useful in blocking sources of undesirable behavior such as brute force attacks on password mechanisms, spammers (by hooking it up to your mail server's rejection log), as well as hostile vulnerability scanners. However, it only works for IPv4. Discussions (and patches) I've seen to make it work with IPv6, unfortunately focus on making it understand IPv6 addresses, and miss an important point. With IPv6, entities, even home users, will have large networks at their disposal. As a result, it may be futile to block a single IPv6 address. However, blocking whole IPv6 networks with the same threshold as a single IPv4 user may block legitimate users. I need a program that will work like fail2ban but will allow progressive blocking, as follows: If undesirable behavior is observed from IP addresses within a network of size N past threshold T(N), block the entire network. This would work with multiple network sizes, starting with singleton IPs and scaling up to large networks, with the threshold increasing and being more tolerant the larger the network is. How the threshold changes with the size of the network should be configurable.

A corollary of the above is that when we'll move to IPv6, as some service providers have already done, password strength, and the strength of secrets and applications in general, will have to increase because we will have to be more tolerant of undesirable behavior, until the threshold of the attacker's network size is reached. This will of course be likely a lot more, and at a minimum the same, as what we tolerate on IPv4 for a single address.