My wife gets this all the time surfing BayKoreans.net and trying to stream videos off of there. I found a way you can get rid of it without losing your current tabs open in Safari:
1. Force quit Safari by double-pressing Home button and swiping up on Safari
2. Open Safari, and as it loads the page, quickly press multiple times the area where the tabs button (overlapping squares icon) will appear to show tabbed view, you'll still get the "Cannot Open Page" error
3. Force quit Safari one more time by double-pressing Home button and swiping up on Safari
4. Open Safari, and as it loads the tabbed view, press on any other web page by quickly pressing multiple times over another tab to cause it to load a different web page
5. Once Safari correctly loads a page without the scam/error, go back to tabbed view by pressing the tab button (overlapping squares icon)
6. Close down the offending site that caused the error by pressing the little "x" on the tab with the error
This method perserves your tabs and history, so it's a preferred for my wife who always has a bajillion tabs open to various sites.
Another option, which I'm experimenting if it'll work, is to put a keyword filter for "IOS Security Breach" in your firewall on your router. Not all routers will support this feature however. If your router supports blocking websites with keywords you can prevent multiple devices from getting these errors on your network. Every router setup is different so I can't give specific instructions on how to do this, but you can find out by Googling "how to block websites [YOUR_ROUTER]" where [YOUR_ROUTER] is the model of your router. So for example if you have a NetGear Nighthawk router you could Google: "how to block websites netgear nighthawk". You should find instructions near the top of the search results.
Hope that helps,
Charley
