- When users mistype a domain name, they are sometimes directed by their ISPs to a placeholder Web site with generic advertisements. This is typically an additional revenue source for the ISP. In the case of CNC, customers of this prominent ISP are directed to a Web site under the control of an attacker.
Websense provided screenshots of an nslookup of a potential mistyped URL. The first shows an unaffected name server, while the second shows the poisoned name server: Unaffected name server: Poisoned DNS server: A user querying an unaffected DNS server is taken through to a clean site but if the target queries a poisoned name server, the browser is redirected to the attacker's site with the malicious iFrame code: