How to blackhole IP's at the server level:
Generic (should work on any unix OS)
/sbin/route add IP 333.444.555.666
Generic Linux
/sbin/route add -host IP gw 333.444.555.666
Newer versions of Linux support the reject flag now. (I believe kernel 2.2+)
For linux users, try this one first...if it tells you reject is not a valid flag, use the generic one.
/sbin/route add -host IP reject
Generic BSD (BSDI, OpenBSD, NetBSD, FreeBSD)
/sbin/route add IP 333.444.555.666
Generic Sun
/usr/sbin/route add IP 333.444.555.666 1
NEXTSTEP
/usr/etc/route add IP 127.0.0.1 1
FreeBSD
route add -net IP -netmask 255.255.255.255 127.0.0.1 -blackhole
Digital UNIX 4.0D (OSF/1 / Compaq Tru64 UNIX)
/sbin/route add -host -blackhole IP 127.0.0.1
where "IP" is replaced with the IP you want to block.
(courtesy of the
iprotect docs)