The hack accomplished by Turkguvenligi is a powerful one. Although it appears the goal of the group was just to vandalize the sites for a while, the group could have set up lookalike sites for the real ones, tricking users into thinking they were on the legitimate site and possibly stealing logins and passwords.

Two of HSBC's banking sites -- one with a country-code Top Level Domain in South Korea and one in Canada -- were targeted, according to the list compiled by Zone-H.

Other websites affected were those belonging to The Telegraph newspaper, The Register technology news site, Coca-Cola, Interpol, Adobe, Dell, several Microsoft country sites, Peugeot, Harvard University and the security companies F-Secure, BitDefender and Secunia. The website for Gary McKinnon, the so-called NASA hacker who is appealing extradition to the U.S. on hacking charges, was also hit.

The Register wrote that its website was not breached and that service was restored about three hours after the attack.

"As far as we can tell there was no attempt to penetrate our systems," . "But we shut down access/services - in other words, anything that requires a password - as a precaution."