If a sql server is allowed to be accessed from any outside IP, and if windows event logs numerous (wrong) login attempts from unauthorized ip addresses/uses, does it influence sql server performance?
For example I detected approx 100 login tries during a period of one second, and I really want to know does it influence performance (and how), before I whitelist Ip addresses allowed to access sql server.
It likely does, but NOT in a way that is relevant for you. I.e. if I would start saturating the internet link with thousands or tens of thousands of login attempts PER SECOND then likely logging would slow down the system disc and your internet bandwidth would suffer.
A smallish number of login attempts (like hundreds per minute) are a non issue.
Still you violate best practices - reduce your attack surface.