Expect more of the same from South Korea in the weeks, months, and (unfortunately) years to come. These massive attacks have been happening for many years now, and nobody seems to have learned a thing.
The latest news here in Korea says that bank employees' PCs were infected through a compromised third-party package management system. Only two years ago, 35 million accounts at one of South Korea's most popular social networking services was compromised through a similar route: the attackers broke into the update servers of a popular antivirus software, which was used on employees' PCs. Same story, only with different companies.
And of course, by "PC", I mean machines running Windows XP with the user always logged in as administrator and IE's security setting somewhere between Medium-Low and Low, because how else are you going to browse the ActiveX web? The companies that provide package management systems and antivirus software probably also use similar PCs, which is likely to be one of the reasons why they got compromised in the first place.
Macs are getting popular nowadays among chic teenagers and college kids, but on the other hand, a long-time member of an IT forum that I frequent recently asked whether he should upgrade from IE6 to IE8 on his primary computer. We might make the best Android phones in the world, but the rest of South Korea's IT infrastructure is nothing but a series of facepalms.
And the first thing the leaders do is blame North Korea. Which they have been doing every time something similar happened in the last 4-5 years. I don't know whether it's actually NK or not, but as for improving the system, nope, my brother's university still asks him to disable several of IE9's security measures every time he logs in.