Microsoft Active Directory is prone to a remote code-execution vulnerability. Attackers can exploit this issue to execute arbitrary code in the context of the application. Successful exploits will completely compromise the affected computer. Failed attacks will cause denial-of-service conditions.
Block external access at the network boundary, unless external parties require service.
If global access isn't needed, filter access to the affected computer at the network boundary. Restricting access to only trusted computers and networks might greatly reduce the likelihood of successful exploits.
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. This includes but is not limited to requests that include NOP sleds and unexplained incoming and outgoing traffic. This may indicate exploit attempts or activity that results from successful exploits.
Implement multiple redundant layers of security.
Memory-protection schemes (such as nonexecutable stack and heap configurations and randomly mapped memory segments) will complicate exploits of memory-corruption vulnerabilities.
The vendor has released an advisory and updates. Please see the references for details.