The Gyeongin Daecheop(Metal Tiger Great Victory) (경인대첩(庚寅大捷)),¹⁾²⁾ also known as the March 1st F5 Attack (三・一F5アタック), was a civilian-organized, cyberwarfare campaign between Japanese and South Korean internet communities that occurred in the month of March 2010.

In retaliation for inappropriate Japanese commentary on 2channel regarding the Korean exchange students attacked by Russians in Barnaul^3)4)5)6) and Yuna Kim's success in the 2010 Winter Olympics,⁷⁾ several Korean internet communities would unite with the goal of launching an attack on 2channel, setting up their attack bases on websites like DC Inside and Naver on February 24, 2010.⁸⁾

Of course, someone ended up warning 2channel about the imminent attack planned for March 1, 2010, the March 1st Movement's anniversary,⁹⁾ so both sides tightened up security. When Yuna Kim won gold, a Japanese false-flag attack was conducted on 2channel's “Yaoi” (/801/) board¹⁰⁾ to justify attacking DC Inside, but the Koreans were busy celebrating and the attacks didn't do much.

After looking at weapons historically used against 2channel, Korean programmers unleashed “KPS2”¹¹⁾ and “UDP Flooder” on the day of the attack. In short, the Korean community had a massive advantage as their national holiday fell on a weekday and quickly managed to overload 2channel's servers. Despite their attempt to mitigate the damage,¹²⁾ people could see that all of their servers went down by 5:00pm.¹³⁾¹⁴⁾

The management raised a white flag and the 2channel community was not in a position to fight back, so the Japanese effectively surrendered at 8:43pm and the Koreans declared victory at 9:38pm with their forces beginning to disperse. Some light skirmishes followed, including a Japanese occupation of Thredic, yet these attacks are mere footnotes compared to the attack on 2channel.

After the war concluded, both sides wondered if the conflict would reignite, but neither side wanted to make the first strike despite the Liancourt Rocks dispute, recent trade dispute, and boycotts that would come in the following decade. Some analysts suggest that the war reflected internet culture at the time, so it would be unlikely for modern conflicts to escalate to DDoS and raids in this day and age.

• Japan and South Korea both used UTC+09:00 in 2010, with neither party observing DST.
• When the plan leaked, Naver added a membership question and DC Inside added a rather intimidating CAPTCHA to deter spies whose answer was reference to a then-viral Nongshim commercial.¹⁵⁾
• NTTEC (PIE), the company that maintained 2channel's servers, initially described their campaign as a “primitive F5 reload attack” (原始的なF5リロード攻撃).¹⁶⁾ After the servers went down, they changed the story to a “mass amount of bot computers”, and claimed that all of the documented information had been forwarded to the “local authorities”¹⁷⁾ around March 2, 2010 at 12:03am.¹⁸⁾¹⁹⁾
  • Japanese media would spread rumors that the FBI was involved and estimated $2.5 million USD in damages,²⁰⁾²¹⁾ but this issue is that the estimate came out way too quick and the FBI probably wouldn't get involved as it wasn't directly targeting a U.S. entity. Theoretically, this issue would have to be raised to the CIA, in cooperation with South Korea's NIS and Japan's CIRO.
• On March 2, 2010, it was reported that the ROK Air Force had crashed two F-5 jets.²²⁾²³⁾ Some Japanese nationalists may claim that this war ended in a “tie” despite having zero involvement.
• There were plenty of Japanese text artwork involving Nida, but most of these offer an extremely biased side of events with the “F5 attack” narrative, so I've opted not to display them in this article.
• Sankaku Complex is not a news source. The website mostly echoed the Japanese perspective by framing Koreans as nationalists (omitting the Barnaul attacks),²⁴⁾ echoing a damage estimate from the right-wing Sankei Shimbun,²⁵⁾ then they suddenly defend “freedom of speech” out of nowhere.²⁶⁾
• By coincidence, 2010 was the 100th anniversary of the controversial Japan–Korea Treaty of 1910, where Imperial Japan arguably coerced the annexation of the Korean Empire.

• 2010 Japan–South Korea cyberwarfare on Wikipedia [EN]
• 2010 March 1st Cyber War on Namu Wiki [KO]
• March 1st F5 Attack on Niconico Encyclopedia [JA] - Warning for extremely transparent racism.