Thinking About Security When Running a Hobby Server

1. Why the VPS company forcibly shut down the server I used as a hobby

Recently, the VPS server I had been using as a hobby was suddenly and forcibly shut down. This was because my server had been used to attack other sites.

At this point, it was almost certain that the forced shutdown would lead to the contract being terminated.

2. The server's recent problems and the warning signs I missed

Before the forced shutdown, there were many times when I felt the server was not working properly. However, I did not realize these were signs of unauthorized access.

1) About two months earlier, I logged in via SSH and accidentally restarted the server from the VPS control panel. After that, I could no longer log in via SSH, and even reissuing the private key did not let me log in. Because it was not a Docker environment and reinstalling would have been time-consuming, I did not consider reinstalling as an option.

2) I decided to use FTP and Telnet instead of SSH.

3) I repeatedly received emails from the server monitoring service I had signed up for, saying that the server had gone down multiple times within short periods.

3. The fact that the server had been misused to attack other sites

The investigation revealed that my server may have been misused by a third party and used for DDoS attacks on other sites.
Several other types of attack are also possible.

4. Future countermeasures and considerations

I have now sent an email to the VPS representative explaining that I was not the one carrying out the attacks. I am still considering how to respond going forward, but in light of this incident, strengthening security measures is essential. I am also looking into appropriate procedures for the future. These efforts are indispensable for ensuring safety and reliability going forward.