csigncsign on "[Plugin: Wordfence Security] What does this mean: "Exceeded the maximum number of page not found errors ..."?"

Hi,

I'm using WP 3.9.1 network installation, Wordfence 5.0.9 network-enabled.

Every day I get for all my blogs within the network several (!) e-mails with the same text, but different IPs like this one:

Wordfence has blocked IP address 140.237.22.105.
The reason is: "Exceeded the maximum number of page not found errors per minute for humans.".
User IP: 140.237.22.105

It's really annoying. What does this mean and what to do?

Thanks.

https://wordpress.org/plugins/wordfence/