在使用国外的VPS向国内传输文件的时候，使用SCP的时候遇到下面这个问题：

IT IS POSSIBLE THAT SOMEONE IS DOING SOMETHING NASTY! Someone could be eavesdropping on you right now (man-in-the-middle attack)! It is also possible that the RSA host key has just been changed. The fingerprint for the RSA key sent by the remote host is a4:e9:24:22:b2:4d:e3:dd:f7:50:de:3d:b9:65:5c:72. Please contact your system administrator. Add correct host key in /root/.ssh/known_hosts to get rid of this message. Offending key in /root/.ssh/known_hosts:4

删除了国外VPS上的 /root/.ssh/known_hosts文件，或者清空即可。

SCP走的协议是跟SSH一样。