The proxy settings need to be configured in 2 locations on the DCS Manager machine:

1- To download Titanium information, SymEFA and Revocation lists:

Browse to <Server installation folder>\liveupdate 

and start command prompt.

"..\jre\bin\java.exe" -classpath jlu.jar com.symantec.liveupdate.config.editor.ConfEditor

A new dialog box opens.

In the dialog box, add a new property as:

Property name: proxy.
Property value: proxyhost:proxyport.

Click Ok

Click Save

2 - To download Reputation Data:

Go to <Server installation folder>\Symantec\Data Center Security Server\Server\tomcat\conf\

Edit sis-server.properties 

Add the following lines (they are already present but commented out with #)

sisserver.http.proxyset=true

sisserver.http.proxyhost=192.0.2.2

sisserver.http.proxyport=3128 

Save and exit.