DNS Calc is a technique in which the octets of an IP address are used to calculate the port for command and control servers from an initial DNS request.   
Detectable by Common Defenses (Yes/No/Partial): No
Explanation: There are not currently available tools that provide the ability to conduct this calculation to detect this type of activity.
Difficulty for the Adversary
Easy for the Adversary (Yes/No): Yes
Explanation: This technique assists the adversary in bypassing egress filtering designed to prevent unauthorized communication. It has been used by APT12, but not otherwise widely reported. Some botnets are hardcoded to be able to use this technique.
- Adam Meyers. (2013, March 29). Whois Numbered Panda. Retrieved March 6, 2017.
- Ned Moran, Mike Oppenheim. (2014, September 3). Darwin’s Favorite APT Group. Retrieved March 6, 2017.
- nex. (2013, August 26). Upcoming G20 Summit Fuels Espionage Operations. Retrieved March 6, 2017.