It's used extensively in djb's packages like qmail and ucspi-tcp. In the latter, it's used to maintain a database of blacklisted IPs which are blocked from conn

It's used extensively in djb's packages like qmail and ucspi-tcp. In the latter, it's used to maintain a database of blacklisted IPs which are blocked from connecting to a TCP server, among other things. http://cr.yp.to/cdb.html http://cr.yp.to/cdb.html