A strange IP Address has accessed my host.

An unfamiliar IP address accesses my host-Linux Enterprise Application-Linux server application information. The following is a detailed description. I used the FC system. I did not shut down the system last night due to the yum upgrade.
In the morning, the desktop prompts FFFF: //// xxx. xxx. xx. xxx to remotely log on to my desktop system.

It's a lot better to have those photos with friends on the CD.

Since this talent started to get started with LINUX, he was not very familiar with the entire system.
So I am worried about security issues. I don't want my system to be like a public toilet. If someone else wants to come, they can leave!

Thank you!