and, in a later message:
Someone gained access to your machine. The attacker had (probably still has) the right to change files on your machine. This particular file seems to be clean at this moment, but you don't know what else they are doing that you are NOT seeing at this point.
Typical intrusion points are insecure PHP scripts and forms.
Please consider what someone can do who has file writing privileges on your server:
- use your machine as a storage space for file sharing (read: distribute illegal copies of new movies)
- use your machine to store and share child porn
- use your machine to send out millions of spam mails
- add your machine to a botnet and rent it for attacks (as in: blackmailing online businesses with DDOS attacks)
- download confidential info from your machine like credit card info, passwords
- use your machine as a landing platform for online fraud
They could as well use a new email account @your-machine.com.
You, as the owner of the machine, will be held responsible for all this.
Security has been breached on your system. There is only ONE reasonable reaction to this. As the system is compromised, it ought to be set up again from scratch, which means above anything else the underlying operating system must be re-installed. Afterwards, your HTML files can be copied back onto the machine.