South Korea's communication watchdog said Wednesday that massive computer network failures at major broadcasters and banks were caused by hacking attacks using malignant code.

Officials said they could not find any evidence to link the attacks to North Korea but stressed that does not mean that they are ruling out such a possibility.

At around 2 p.m., broadcasters KBS, MBC and YTN and four banks -- Shinhan, Nonghyup, Woori and Jeju -- reported to the National Police Agency (NPA) that their computer networks were entirely halted for unknown reasons.

Following an analysis of malicious source codes, the Korea Communications Commission (KCC) said it believes the codes were distributed via patch management systems, which are used as update servers.

The KCC, however, said the network failures were not caused by distributed denial-of-service (DDoS) attacks and did not confirm whether North Korea was involved in the incident.

Following the network paralysis, the communications watchdog issued a "caution" alert on cyber attacks, the third highest on a five-notch scale.

Under a "caution" alert, the government triples its monitoring workforce and organizes a government-wide investigation team to launch on-site inspections.

The KCC said the government task force has been dispatched to the affected broadcasters, Shinhan Bank and LG Uplus Corp. for on-site inspections.

No damages have been detected at state and public institutions and infrastructure, it added.

The government plans to hold a state strategy meeting on cyber security and discuss countermeasures once the reasons for the paralysis are clarified, the KCC said. (Yonhap News)