To conceal the values -Dhttp.proxyHost -Dhttp.proxyPassword parameters from the process list (ps aux),

Refer to Configuring Web Proxy Support for Confluence. Rather than declare the -Dhttp.proxyPassword parameter as a JAVA_OPTS, you can declare it in the catalina.properties file:

http.proxyHost=yourProxyURL
http.proxyPort=yourProxyPort
http.proxyUser=yourUserName
http.proxyPassword=yourPassword

Then set appropriate permissions on the properties file to protect the plaintext password.