Question

I'm using the below open DNS name servers which I got from a friend. Are they trustable?

4.2.2.1, 4.2.2.2, 4.2.2.3, 4.2.2.4, 4.2.2.5, 4.2.2.6

Answer 1

Those are open DNS servers - i.e. they're on the public internet. They belong to Level 3 so are probably safe to use.

OpenDNS (note no space) is another DNS provider which has different addresses for it's public servers, which are in harrymc's post.

Answer 2

According to opendns.com:

OpenDNS nameserver IP addresses are:

208.67.220.220
208.67.222.222

Some routers and devices need a third or fourth nameserver IP address. Use these if necessary (identical service to the original two):

208.67.220.222
208.67.222.220

Answer 3

They have nothing to do with OpenDNS (see Dave Webb's post) and, since they are open recursive name servers, they should not be trusted:

• risk of being shut down at every moment, because they can be used for amplification attacks (see RFC 5358)
• much higher risk of poisoning through the Kaminsky weakness (since a prerequisite of the Kaminsky attack is the ability to use the name server).