As now a days we use dynamic media so we do not need assets on publish environment.
In order to restrict the DAM asset activation we have done following steps:
1. Create a user on every environment's author instance with full access excluding access on /content/dam/. For now we have created a user named replication-user.
2. Go to replication agent of the author
3. Click on edit, on the model window add the name of the user created in Agent User ID field and click on ok.
4. Now when you publish any asset under/content/dam/ it will not be replicated to the publish instance from the author environment.
@kautuk_sahni This will restrict even metadata of the images from publisher right? Is there anyway if we need metadata in publishers but not the assets? Because usually we have lot metadata including title/alttext which is needed to build an image component.