Building Firewalls with OpenBSD and PF, 2nd edition

Written by Jacek Artymiak, a frequent contributor to ONLamp.com, Building Firewalls with OpenBSD and PF is the first and only print publication devoted solely to the subject of the pf packet filter used in OpenBSD, FreeBSD, and NetBSD operating systems. Topics covered include: firewall design, ruleset syntax, packet normalization (scrubbing), packet redirection (masquerading), packet filtering, bandwidth management (ALTQ), load balancing, and more. The author maintains a web site and a mailing list for the readers of his book.