Answer: Internet Explorer

If you don’t live in South Korea, the very concept might seem pretty bizarre: a mandatory web browser. But for millions of South Koreans, using Internet Explorer is pretty much obligatory. While citizens are free to use a different web browser for their own personal browsing (like, say, reading How-To Geek), any government business, banking, or shopping must be done using Internet Explorer.

Why Internet Explorer? South Koreans can thank an outdated security law from 1999. In an effort to provide better cyber security for their country, Korean legislators passed a law requiring government websites and commerce sites to accept digital certificates and, in turn, for each citizen to have their own unique digital certificate which functions like a virtual ID card. The certificates require ActiveX, a Microsoft plugin, and ActiveX, in turn, requires Internet Explorer.

While this setup is inconvenient enough as it stands (after all, what are OS X users, who don’t have Internet Explorer and ActiveX supposed to do), it also poses a security risk. In early 2016, South Korea was slammed with a targeted zero-day exploit that relied on a vulnerability in Internet Explorer–given the sheer concentration of people all using the same browser, the country makes for an irresistible target.