Microsoft Exchange Server is prone to a vulnerability that may let attackers execute code remotely. This issue is exposed when the server handles emails that contain malicious calendar data that is included in meeting requests. If the issue is successfully exploited, this could completely compromise the computer hosting the mail server.
Disallow anonymous access to services. Permit access for trusted individuals only.
If appropriate for the organization, require authentication for email clients. While this will eliminate the risk of anonymous attacks, the server will still be vulnerable to attacks by authenticated users.
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 exploitation attempts or activity that results from successful exploitation.
Implement multiple redundant layers of security.
Memory-protection schemes such as non-executable stack/heap configurations and randomly mapped memory segments may complicate exploitation of various code-execution vulnerabilities.
Microsoft has released a security bulletin to address supported versions of Microsoft Exchange Server.