I have a list of IP addresses and I want to find out their owner. In many cases dig returns the name of their carrier for example AT&T. Is there a way to overcome this and find the company at which the IP is registered?
search here: http://whois.arin.net/ui/ (search box in the upper right)
The Internet IP addresses are managed by the IANA: Internet Assigned Numbers Authority
IANA assign block of IP addresses to the five Regional Internet Registry (RIR)
African Network Information Center (AFRINIC) for Africa.
American Registry for Internet Numbers (ARIN) for the United States, Canada, several parts of the Caribbean region, and Antarctica.
Asia-Pacific Network Information Centre (APNIC) for Asia, Australia, New Zealand, and neighboring countries.
Latin America and Caribbean Network Information Centre (LACNIC) for Latin America and parts of the Caribbean region.
Réseaux IP Européens Network Coordination Centre (RIPE NCC) for Europe, Russia, the Middle East, and Central Asia
The RIR, in turn assign smaller blocks of IP address to Local Internet Registry (LIR) which usually are Internet Service Providers (ISP).
Then the ISP allocated IP addresses to their customer.
The LIR is responsible for maintaining information about IP address usage in the LIR database. It is in those databases that you can get the official information about a given IP address usage.
So to found out who currently use an IP address, you first have to found out to which LIR it was assigned to by IANA. You can do so on this page : IANA IPv4 Address Space Registry for IPv4 or this one for IPv6: IPv6 Global Unicast Address Assignments
Or, more conveniently, you can search directly in the North-American LIR, ARIN, database on this tool : Whois-RWS
If the network was allocated to ARIN then you will directly have the answer, otherwise it will show to which LIR the network was allocated and a link to the LIR search page in the resources section.