SEOUL, Jan. 17 (Yonhap) -- North Korea is suspected of masterminding last year's attempt to hack into the e-mail accounts of a Seoul university's graduate school alumni, school officials said Tuesday.

The Graduate School of Information Security at Korea University said it has conducted a joint investigation with intelligence authorities to track the origins of the hacking attempt, upon learning that an e-mail carrying malicious codes was sent to some of its graduates via its internal e-mail accounts last November.

"The e-mail was found to have been sent from a server based in Taiwan often used by North Korea," a school official said, declining to be identified.

"But no damage has been reported, as our graduates who received the e-mail never opened the file attached, and the codes did not work well from the first place," he added.

The malicious code can reportedly infect the computer of the recipient, and give hackers access to the user's e-mail exchanges.

The school authorities said they blocked the graduate school's separate e-mail server to integrate all the accounts with the university's server, which is equipped with a relatively stronger protection system as part of efforts to beef up security.

North Korea has recently launched several cyber attacks on the South, crippling the computer networks of a major local bank and attacking the web sites of the presidential office and other government agencies last year.