Turkish hackers have attacked the domain name systems (DNS) of seven prominent web sites including those of Vodafone, Betfair, Acer and news sites the Telegraph and the Register.
Visitors to the sites, which also included UPS and National Geographic, were redirected to hacking group TurkGuvenligi.info's page overnight.
TurkGuvenligi.info changed domain name records of several registrars to redirect vistors who used human-readable web addresses – such as www.vodafone.com.
The hack did not not affect visitors attempting to reach the websites through their IP addresses.
TurkGuvenligi.info took responsibility for the attacks and posted mirrors of the defacement on hacking league table Zone-H.
The Register said in a statement that user records were not affected. It had shut down user portals as a precaution.
DNS records have since been restored.
TurkGuvenligi.info was responsible for a string of hacking incidents including a similar DNS attack last month that affected 100,000 Korean websites.
In 2010, the group defaced web sites of Harvard University, Microsoft Israel, Kaspersky, BitDefender, NASA, Coca-Cola and Hotmail, as well as an Australian Peugoet website.