said by RolteC:Thanks rtcy, I actually already use OpenDNS. Unfortunately, people are setting their own DNS servers.
you mean on computers inside your house/network correct ? cause if you know what ip's they are using you can block them , or just make a list of open public dns servers and see if they complain. and just make sure your edge router is set under connections wan ethernet / or coax whatever you are configured for to only 208.67.220.220 and 208.67.222.222 and when their entries fail on their computers it will drop to whatever the router feeds them and they will never know it
the more server numbers you block at opendns the more control you will have here is a small list
8.8.8.8
8.8.4.4
156.154.70.1
156.154.71.1
198.153.192.1
198.153.194.1
4.2.2.1
4.2.2.2
4.2.2.3
4.2.2.4
4.2.2.5
4.2.2.6
67.138.54.100
207.225.209.66
85.88.19.10 (German Xail.net) sehr schnell!
85.88.19.11 (German Xail.net)
87.118.100.175 (German Privacy Foundation e.V.)
94.75.228.28 (German Privacy Foundation e.V.)
62.141.58.13 (German Privacy Foundation e.V.)
85.25.251.254 (German Privacy Foundation e.V.) langsam!
85.214.73.63 (FoeBuD e.V.)
212.82.225.7 (ClaraNet)
212.82.226.212 (ClaraNet)
213.73.91.35 (Chaos Computer Club Berlin)
58.6.115.42 (OpenNIC, Australien)
58.6.115.43 (OpenNIC, Australien)
119.31.230.42 (OpenNIC, Australien)
200.252.98.162 (OpenNIC, Brasilien)
217.79.186.148 (OpenNIC, Deutschland)
82.229.244.191 (OpenNIC, Frankreich)
216.87.84.211 (OpenNIC, USA)
2002:d857:54d2:2:20e:2eff:fe63:d4a9 (OpenNIC, IPv6 USA)
2001:470:1f07:38b::1 (OpenNIC, IPv6 USA)
2001:470:1f10:c6::2 (OpenNIC, IPv6 USA)
66.244.95.20 (OpenNIC, USA)
204.152.184.76 (f.6to4-servers.net, ISC)
2001:4f8:0:2::14 (f.6to4-servers.net, IPv6, ISC)
194.150.168.168 (dns.as250.net; anycast DNS!)
80.237.196.2 (Erdgeist)
194.95.202.198 (UDK Berlin)
88.198.130.211 (Dataflash)
78.46.89.147 (ValiDOM)
129.206.100.126 (URZ Uni Heidelberg)
79.99.234.56 (justnet.ch, Schweiz)
208.67.220.220 (OpenDNS)
208.67.222.222 (OpenDNS)
156.154.70.22 (Comodo Secure DNS)
156.154.71.22 (Comodo Secure DNS)
85.25.149.144 (Freie DNS-Server)
87.106.37.196 (Freie DNS-Server)
8.8.8.8 (Google Public DNS)
8.8.4.4 (Google Public DNS)
88.198.24.111 (jali/CCCHB)
you can google tons of them block em ALL