Remotely exploitable vulnerabilities have been identified & published in NTP (network time protocol). This is often a CRITICAL protocol/instance for ICS environments and can be widely located in many control networks.
The fix currently appears to be an upgrade to 4.2.8 or later.
This should be considered a HIGH PRIORITY for critical infrastructure networks. Exploits are expected as this is an unauthenticated remotely triggered buffer overflow, which should be easily implemented into existing exploit kits.
Please let us know if we can assist you in any way. Stay safe out there!
Update: 12/19/14 2pm Eastern – According to this article, exploits are now publicly available.