T1568.003: DNS Calculation

Adversaries may perform calculations on addresses returned in DNS results to determine which port and IP address to use for command and control, rather than relying on a predetermined port number or the actual returned IP address. A IP and/or port number calculation can be used to bypass egress filtering on a C2 channel.

One implementation of DNS Calculation is to take the first three octets of an IP address in a DNS response and use those values to calculate the port for command and control traffic.

Positive Technologies products that cover the technique

Description of detection methods is not available yet

Detection

IDDS0029Data source and componentNetwork Traffic: Network Traffic ContentDescription

Monitor and analyze traffic patterns and packet inspection associated to protocol(s) that do not follow the expected protocol standards and traffic flows (e.g extraneous packets that do not belong to established flows, gratuitous or anomalous traffic patterns, anomalous syntax, or structure). Consider correlation with process monitoring and command line to detect anomalous processes execution and command line arguments associated to traffic patterns (e.g. monitor anomalies in use of files that do not normally initiate connections for respective protocol(s)).