Recently beyondpluto created a chrome extension which paints every day in the calendar with the color of the hardest problem solved in that day. You can read about it here: https://mirror.codeforces.com/blog/entry/140881

And I've just realized: that it's the greatest tool for catching streak frauds! Here is the meme depicting what I mean:

Post similar frauds in the comment! And huge thanks to beyondpluto for this extension!