export ftp backup security

[domotiqa]

Hi,
I would like to backup every month the LM  of all my customer.

Can you give advice in order not to have security issue.
I was thinking about encoding the password, but it's still quite simple to revert the ftp password with basic IT skills.
I don't want people who have acces to the admin part to be able to take control of the ftp.
regards

Code:

-- load the ftp support
local ftp = require("socket.ftp")
local ltn12 = require("ltn12")

-- ftp to NAS
f, e = ftp.put{
  host = "xxxx",
  user = "xxxx",
  password = "xxxx",
  type = "i",
  argument = target,
  source = ltn12.source.file(io.open(dst, "rb"))

}
if (e) then
  log (e)
  log (f)
  alert("Could not ftp: ", e, "\n")
end
log("ftp_backup")