Hi Fabrice,
Yes, this is a Helix 3 based template.
Please make sure you update both the Helix 3 System Plugin and the Helix 3 Ajax Plugin to the latest versions.
For Joomla 3.x sites, this will provide basic protection, but keep in mind Joomla 3 is end-of-life, so security is limited compared to newer Joomla versions.
We also strongly recommend upgrading to the latest Joomla version and updating SP Page Builder to v6.6.2 for improved security and compatibility.
You may also find this discussion helpful, you can not update sp page builder to the latest due to hosting limitations: https://www.joomshaper.com/forum/question/45258
You can also use the following security scanner to help identify malicious files and delete them: https://github.com/zkrana/joomla-security-scanner
Please make sure to read the README.md file in the repository for instructions on how to run the tool.
After completing the cleanup and upgrading to v6.6.2, please let us know the outcome or if you need any further assistance.
We'll be happy to help.
Thank you.