Protecting documents with security overlays

A method comprises:

• providing a first code module on a computing device having a plurality of policies wherein the plurality of policies control access to a plurality of documents;
• providing a second code module on the computing device having an ability to augment display content, wherein the second code module is installed in a compositing window manager;
• detecting by the first code module an attempt by an application program on a computing device to access a document;
• selecting by the first code module a subset of policies from the plurality of policies relevant to the attempted access to the document;
• evaluating by the first code module the subset of policies to determine if the attempted access to the document should be allowed;
• if the attempted access to the document is allowed, transmitting by the first code module information related to the attempted access to the document to the second code module;
• if the attempted access to the document is allowed, constructing a security marker based on the information related to the attempted access to the document;
• if the attempted access to the document is allowed, rendering the security marker by the second code module over content of the document;
• and
• if the attempted access to the document is not allowed, blocking the attempted access to the document.