The attack, apparently carried out by someone working under the name "Dinam," who claimed in his online posting to be Turkish, was brought to the attention of Silicon.com last Thursday.
The defacement was removed from Apple's Web site shortly after Silicon.com alerted the company, which has subsequently declined to comment on the matter.
Jason Hart, CEO of security company Whitehat UK, told Silicon.com: "The defacer has managed to get administrator access to the Web server."
Although Hart said he suspected that the hacker was after little more than "self-gratification" from vandalizing the site, he said Apple should communicate what happened to its customers to end speculation.
"The worst thing Apple can do is not tell customers what has happened," Hart said. "It's like all the big companies though--they're constantly having to defend themselves, as they're being probed all the time."
The defacement--which took the form of a dozen lines of code posted to the Apple.co.kr home page--was documented on Zone-h.org. The hacker forum said Dinam had attacked a Mac OS X server running Apache.
"Defacements are not that big a deal, provided the customer data has not been disclosed or they have suffered an economic impact," Richard Starnes, president of the Information Systems Security Association UK, said.
"Defacements just tend to be embarrassing. But we know Apple is a good company and takes defacements seriously," he added.
Dan Ilett of Silicon.com reported from London.