ICANN, the organisation that oversees the web's top-level domain naming system, has said that the hijacking last month of several of its domains was due to a security breach at the registrar that manages those URLs.

Although it did not name the registrar explicitly, according to WHOIS searches, New York-based Register.com manages the domains that were redirected, as well as the primary icann.org and iana.org domains.

Two weeks ago, Turkish hackers rerouted traffic to some of the domains used by ICANN (Internet Corporation for Assigned Names and Numbers) and one of its subsidiary organisations, IANA (Internet Assigned Numbers Authority).

Visitors who intended to reach iana.com, iana-servers.com, icann.com and icann.net on 26 June were instead shunted to an illegitimate destination, which displayed a taunting message: "You think that you control the domains but you don't! Everybody knows wrong. We control the domains including ICANN! Don't you believe us?"

Through its IANA subsidiary organisation, ICANN manages the DNS root zone and assigns the DNS operators for the Internet's top-level domains, such as .com and .org. DNS, which translates the domains and URLs - such as computerworld.com - into IP addresses, is a critical component of the web's traffic-guiding infrastructure. ICANN, meanwhile, manages the assignment of domain names and IP addresses.

Although an ICANN spokesman provided a terse explanation shortly after the attack, only last week did the organisation provide more information. In a statement posted to its website on Thursday, ICANN said the attack had been launched against the Internet registrar responsible for the victimised domains, not against the organisation itself.

"The DNS redirect was a result of an attack on ICANN's registrar's systems," said ICANN. "A full, confidential, security report from that registrar has since been provided to ICANN with respect to this attack."

According to ICANN, the attack was two-pronged. "It would appear the attack was sophisticated, combining both social and technological techniques, but was also limited and focused," said the organisation.

"The redirect was noticed and corrected within 20 minutes; however it may have taken anywhere up to 48 hours for the redirect to be entirely removed from the Internet."

While ICANN said it was "confident" that new measures would prevent a repeat embarrassment, it also acknowledged that it had launched an internal review of its security procedures.

Register.com did not immediately reply to a request for comment.