They are supposed to be quite enlightened about all of it: https://en.wikipedia.org/wiki/User:Jasper_Deng/IPv6 Wikipedians are a bit strange that way, they love to block stuff and they definitely do not bother contacting the ISPs involved either, bit of a shame. It is even more annoying as they should really know better. That is up to LeaseWeb, note that 2001:1af8::/32 is theirs, SixXS only is 'borrowing' 2001:1af8:fe00::/40 + 2001:1af8:ff00::/40 for the nlhaa01. Note that all SixXS prefixes are listed in RIPE whois and in whois.sixxs.net. I would not be surprised if that prefix never ended up in WHOIS, does not look like it: whois -h whois.ripe.net -- "--list-versions 2001:1AF8:4700::/48" % This is the RIPE Database query service. % The objects are in RPSL format. % % The RIPE Database is subject to Terms and Conditions. % See http://www.ripe.net/db/support/db-terms-conditions.pdf %ERROR:101: no entries found % % No entries found in source RIPE. % This query was served by the RIPE Database Query Service version 1.73.1 (DBC-WHOIS3) Prefixes that are in WHOIS and where SixxS is responsible will have a proper abuse-mailbox and other details that clearly indicate that it is SixXS's responsibility. Additionally (for ARIN for instance which does not have delegations) they are also in whois.sixxs.net. And yes, you could report something to other abuse addresses, but sending them an email with something like "stuff is blocked at website XYZ" will not get any resolution as there is no actual abuse, especially if it was in the past and you don't even know the time.