Too many Sucuri Alerts, Failed Login

Normal depends on the size of your website, if it big it is probably going to be targeted by a lot of automated vulnerability scanners than many people use to see if your website is vulnerable to something or if one or more of the user accounts have weak passwords.

Go to the “Alerts” panel located in the plugin’ settings page and then uncheck the box named “Receive email alerts for successful login attempts”. Additionally, you can add a plugin to reduce the number of login attempts per username, and/or a firewall [1].

[1] https://sucuri.net/website-firewall/