This article is more than 13 years old

This article is more than 13 years old

Hackers last night mounted the most significant attack since 2002 on the computers that direct traffic on the internet, it emerged today.

The hackers, believed to be from Asia, bombarded the 13 computers, or root servers, that serve as the internet's central address books.

But although the assault lasting several hours was the largest in the past five years, it had little effect on internet users.

"It was a significant and concerted attack, but the average internet user would have barely noticed," said Paul Levins, the vice-president of corporate affairs at the Internet Corporation for Assigned Names and Numbers (Icann), the body that oversees the running of the root servers and the net's addressing system.

"Ironically, the system gets stronger and better because of the attacks as we're constantly upgrading the technology," Mr Levins said.

Hackers periodically try to overwhelm the root servers with requests and information, which can slow down the network response.

The servers are distributed throughout the world and, much like an electricity grid system, can redirect their efforts to where demand is highest.

Root servers manage the internet's domain name system (DNS), used to translate web addresses such as theguardian.com into the numerical internet protocol (IP) addresses used by machines.

When a person types the name of a website into a web browser it looks up the location of that site by consulting a root server.

Two servers seemed to be the target of yesterday's attack, one operated by the US defence department and the other by Icann.

The US homeland security department confirmed it was monitoring what it called "anomalous" internet traffic.

"There is no credible intelligence to suggest an imminent threat to the homeland or our computing systems at this time," the department said in a statement.

The attacks began last night and lasted as long as 12 hours.

"The main thing is that there was very little impact on the general public, the servers were able to hold up against the attacks. The internet in general was designed to even withstand a nuclear attack," Zully Ramzan, a researcher at Symantec Security Response, told CNET News.com.