OpenBSD 4.4 has not been supported for more than a year. The current release is 4.8.
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Because there have been many changes to PF between 4.4 and 4.8, the PF User's Guide available online from the OpenBSD Project website does not have the same exact rule syntax that you may need.
Your choices:
1) Upgrade to or reinstall a supported version of the OS.
2) Extract the HTML files that match a 4.4-release version of the PF User's Guide from the CVS repository.
In both cases, you will need to read the applicable PF User's Guide. You will find a link to the most recent version of the Guide
here.
The rule to prevent certain IP addresses from establishing a connection is the
block filter rule. Lists of IP addresses might be most easily managed in a table. Filter rules are described in their own chapter, as are tables.
As for brute force attacks, yes, you can stop them with stateful tracking options, described in the filter rules chapter. Look for
overload and
flush, and the examples there.