You can switch DirectAdmin to use SSL instead of plain text. -> https instead of http on port 2222.

Creating a Self-Signed Certificate

If you do not have your own certificates, you’ll need to create your own:

/usr/bin/openssl req -x509 -sha256 -newkey rsa:4096 -keyout /usr/local/directadmin/conf/cakey.pem -out /usr/local/directadmin/conf/cacert.pem -days 9000 -nodes
chown diradmin:diradmin /usr/local/directadmin/conf/cakey.pem
chmod 400 /usr/local/directadmin/conf/cakey.pem

Installing a Purchased Certificate

If you already have your own certificate and key, then paste them into the following files:

certificate:  /usr/local/directadmin/conf/cacert.pem
key: /usr/local/directadmin/conf/cakey.pem

Edit the /usr/local/directadmin/conf/directadmin.conf and set ssl=1  (default is 0).  This tells DA to load the certificate and key and to use an SSL connection.
Ensure your directadmin.conf has the values set:

cacert=/usr/local/directadmin/conf/cacert.pem
cakey=/usr/local/directadmin/conf/cakey.pembut can be changed as needed.

DirectAdmin needs to be restarted after any changes to the directadmin.conf.

If you also have a CA Root Certificate, this can be specified by adding:

carootcert=/usr/local/directadmin/conf/carootcert.pem

into the /usr/local/directadmin/conf/directadmin.conf file (won’t exist by default) and by pasting the contents of the caroot cert into that file.