Microsoft Office Web Apps is prone to a remote code-execution vulnerability. An attacker can exploit this issue to execute arbitrary code in the context of the W3WP service account user.
Block external access at the network boundary, unless external parties require service.
If global access isn't needed, block access at the network perimeter to computers hosting the vulnerable application.
Run all software as a nonprivileged user with minimal access rights.
To limit the potential damage that a successful exploit may achieve, run all nonadministrative software as a regular user with the least amount of privileges required to successfully operate.
Deploy network intrusion detection systems to monitor network traffic for malicious activity.
Deploy NIDS to monitor network traffic for signs of anomalous or suspicious activity such as unexplained incoming and outgoing traffic. This may indicate exploit attempts or activity that results from successful exploits.
Implement multiple redundant layers of security.
Since these issues may be leveraged to execute code, we recommend memory-protection schemes, such as nonexecutable stack/heap configurations and randomly mapped memory segments. This tactic may complicate exploits of memory-corruption vulnerabilities.
Updates are available. Please see the references or vendor advisory for more information.