one of the documented procedures in this installation of the ACS
What it does:
Calls ns_conn peeraddr and then tries to figure out if it matches the IP range of a known spammers.
Defined in: /web/philip/tcl/ad-antispam.tcl

Source code:

    set glob_patterns [ad_parameter_all_values_as_list IPglob antispam]
    set client_ip [peeraddr]
    foreach pattern $glob_patterns {
	if [string match $pattern $client_ip] {
	    return 1
    # not a spammer as far as we know
    return 0