The Supreme Court on Thursday upheld a four-year prison term for an aide to a former ruling party lawmaker for launching a cyber attack on the national election watchdog’s Web site during Seoul’s mayoral by-election in October 2011.

The 29-year-old aide to former Saenuri Party lawmaker Choi Ku-sik was found guilty of masterminding the so-called distributed denial-of-service (DDoS) attack on the Web site of the National Election Commission on the eve of the by-election.

In the same ruling, the court confirmed a not-guilty verdict for a 32-year-old protocol secretary to former National Assembly Speaker Park Hee-tae, only known by his surname Kim, on charges of colluding with the former aide, surnamed Kong.

Prosecutors indicted Kong and Kim on charges of ordering computer specialists to execute the attack on the NEC Web site, paralyzing access.

A lower court previously sentenced Kong to five years in prison but an appeals court reduced the term to four years. Kim also previously received a five-year prison term but was acquitted in an appeals ruling, which said that there is not enough evidence that Kim and Kong colluded to launch the DDoS attack.

Since the incident was revealed, opposition parties have raised suspicions that the Saenuri Party masterminded the attacks to block Park Won-soon, then the liberal-leaning candidate in the race, from winning the mayorship of Seoul.

Police, however, concluded that the aides, after hiring computer specialists, launched the attack without any direction from the ruling party. (Yonhap News)