North Korea was accused yesterday of jamming mobile phones and other electronic equipment in the Seoul metropolitan area on Friday in an apparent effort to disrupt joint South Korean-U.S. military drills, military officials in Seoul said.

The disclosure came as concerns have grown over North Korea’s cyberwarfare capabilities. Last week’s cyberattack against South Korean government Web sites is also being examined to see if it had connections to the North.

The Ministry of National Defense said North Korea jammed global positioning system signals in the Seoul area on Friday, causing some electronic devices to malfunction.

Officials said some mobile phones and military electronics used in Seoul and the neighboring cities of Incheon and Paju suffered temporary disruptions at around 4 p.m. Friday. 

“Analysis points to [North Korean] military bases in Haeju and Kaesong near the Military Demarcation Line as the two sources of the jamming,” said a South Korean military official. 

The official said the North blocked GPS signals at intervals of five to 10 minutes. 

The South Korean military believes the North used jamming technology from Russia.

Former Defense Minister Kim Tae-young said at a parliamentary session last October that the North, using the Russian equipment, is capable of blocking GPS signals within 50 to 100 kilometers (31 to 62 miles) of the point of origin. 

North Korea’s motives could be linked to the ongoing Key Resolve/Foal Eagle military drills involving South Korea and the U.S. 

The North threatened harsh action against the South prior to the join drills, which started on Feb. 28. 

This is not the first time North Korea jammed GPS signals during a major military drill in the South. It is believed the North also tried to jam electronic signals during the Ulji Freedom Guardian drill last August. 

The GPS cyberattack comes after another attack last week that temporarily disrupted the Web sites of the Blue House and other key government departments, including the Defense Ministry, Unification Ministry and the National Intelligence Service.

The “distributed denial of service” assaults on about 40 Web sites began on Thursday, although no new attacks were reported yesterday.

DDoS attacks are designed to shut down servers by channeling heavy data traffic to the target Web sites.

Last week’s attacks were similar to cyberattacks in July 2009 against dozens of Web sites in South Korea and the United States. 

South Korean officials later said they suspected North Korea as the source.

Meanwhile, the Korea Communications Commission warned it has detected new types of malicious code, or malware, being distributed over the Internet.

Malware destroys data stored on hard disks and prevents the installation of virus protection programs, the agency said. 

Such malware was found on file-sharing Web sites, including www.superdown.co.kr and www.sharebox.co.kr. 

Computer users in South Korea can download a free program distributed by AhnLab, a computer security company, to diagnose and remove the latest malware.


By Moon Gwang-lip [joe@joongang.co.kr]