To disable SSLv2 server-wide on a Plesk server, add this in your /etc/httpd/conf.d/ssl.conf:

SSLProtocol all -SSLv2

Put the directive very high in the file, outside the VirtualHost directive, preferably right below the Listen directive. This will work for all SSL VirtualHosts.

How can I ensure that Apache does not allow SSL 2.0 protocol that has known weaknesses?