https://codeforces.com/blog/entry/134322

The concept of using proof-of-work to guard against bots is actually clever. Instead of performing some heavily obfuscated tricks to generate a browser fingerprint, or something like that, they simply make the suspected bot perform about a CPU-second of useless computation in order to be granted access. This does not really bother real users, but owners of big bot farms would have to spend colossal amounts of electricity to get access for all of the bots. Instead of preventing automation, this simply makes it impractical enough to attempt.

（以下内容为机翻）

使用工作证明来防范僵尸程序的概念实际上很聪明。他们没有执行一些非常混乱的技巧来生成浏览器指纹或类似的东西，而是简单地让可疑的机器人执行 大约一个CPU秒的无用计算 ，以便被授予访问权限。这并不会真正困扰真正的用户，但大型机器人农场的所有者将不得不花费大量的电力来获得所有机器人的访问权。这不仅没有阻止自动化，反而使尝试变得不切实际。

---

所以说cf真的用了cf盾了吗