isc domain lookup

[Phil Mayers]

On 16/05/14 05:38, Yossi Eskenazi wrote:

> but there are many domains which cannot get through. The problem
> appeared rather recently, so I suspect that an update in a firewall
> brand, or a dns server update is causing this.

Almost certainly not. It's very likely your network provider or one of 
their upstreams put this block in, in response to a reflection attack; 
many attackers sems to use queries for isc.org (and others) for some reason.

Ask your provider what they've done, and to exclude you from it (better 
yet, fix their broken filter)