Something like this?

sudo defaults write /System/Library/LaunchDaemons/com.apple.mDNSResponder
ProgramArguments -array /usr/sbin/mDNSResponder -launchd
-NoMulticastAdvertisements

can be undone with

sudo defaults write /System/Library/LaunchDaemons/com.apple.mDNSResponder
ProgramArguments -array /usr/sbin/mDNSResponder -launchd

Thanks. I already do that but im unsure if this is working or not.

Anyone know if this is working on Mountain Lion?

we just block this using the firewall, as some applications such as final cut composer require mDNS to be running into the work, found that out the hard way, so to stop traffic i just block the port on the client

/usr/libexec/PlistBuddy -c "Add :ProgramArguments:2 string '-NoMulticastAdvertisements'" /System/Library/LaunchDaemons/com.apple.mDNSResponder.plist

sudo defaults write /System/Library/LaunchDaemons/com.apple.mDNSResponder ProgramArguments -array /usr/sbin/mDNSResponder -launchd -NoMulticastAdvertisements can be undone with sudo defaults write /System/Library/LaunchDaemons/com.apple.mDNSResponder ProgramArguments -array /usr/sbin/mDNSResponder -launchd

We've had mixed success with this method in Mountain Lion. The first command will certainly turn it off but the second command doesn't always re-enable it.

Our (test) use case has been to create a "location switcher" launchd item that will turn off mDNSResponder (among other things) when on an untrusted network. When the user reconnects to a trusted network the machine will run the command to re-enable mDNSResponder but we've found that it often doesn't do this successfully.

Honestly, I haven't spent a lot of time troubleshooting the problem as this has been more of a proof of concept than anything we are ready to put into production.

Just thought I'd add some real world feedback with this in Mountain Lion.