According to data collected by Internet infrastructure service RIPE NCC an apparent denial-of-service attack has been launched on two of thirteen root DNS servers early Tuesday morning.

As a cause of the attack these two servers failed to respond to round 90% queries and another server has been seen to suffer from dropped traffic as well. Associated Press reported that a third server has been completely overwhelmed by the attack.

Security experts state that the attacks lasted for at least 12 hours and have been qualified as highly aggressive. Hackers attempted to disguise their origin, however, the vast amounts of traffic have been generated from South Korea.

The attacks appeared to target UltraDNS, the company that operates servers managing traffic for domains ending in ".org".

Tuesday's attack is similar to the one performed in 2002, where 13 root name servers suffered from enormously heavy workload generated by hackers.