When you install Jenkins, the default settings allow anyone to sign up and administer it. There are many ways to secure Jenkins, the simplest is to disable the user sign up and require login to administer the server.
- Click sign up in the upper right corner and create an account for yourself
- On the Jenkins Dashboard select Manage Jenkins
- On the Manage Jenkins page select Configure Global Security
- Make sure the circled items are set according to the picture below.