The virus is written to the file again and again, how to solve?

Question

Joomla

Please help.
There is a site on joomla, of course, with holes in the scripts that I can’t find yet. I decided to just change the file permissions to 500. It seems that files cannot be overwritten with such permissions, but viruses still appear again (js in the head tag). Do I understand correctly that it is necessary to disable the php functions on the server side - popen,dl,set_time_limit,passthru,system,exec,proc_open,shell_exec,proc_close ?

Answer 1

look for better ways to hack
https://spark.ru/startup/miralabs/blog/10191/gajd-...
https://habrahabr.ru/post/226321/

Answer 2

https://www.revision.com/ai/