blackhole(4) on FreeBSD
The text 84d8a49037a3, as FreeBSD 4.11-RELEASE, FreeBSD 4.10-RELEASE, FreeBSD 4.9-RELEASE, FreeBSD 4.8-RELEASE, FreeBSD 4.7-RELEASE, FreeBSD 4.6.2-RELEASE, FreeBSD 4.6-RELEASE, FreeBSD 4.5-RELEASE shipped it.
a sysctl(8) MIB for manipulating behaviour in respect of refused TCP or UDP connection attempts