Domain Generation Algorithms
Where this stands
A reviewer read the telemetry and concluded there is nothing here to detect that a sibling technique does not already cover.
Every discriminator in all three analytics is a statistical property of a set of events, and lib/sigma has no aggregation, no timeframe and no numeric comparison to express any of them. AN1178's knobs are EntropyThreshold (>4.0), QueryFailureRate (>30%) and a 5-10 minute TimeWindow; AN1179's are NXDOMAINThreshold (>40%) and DomainAge; AN1180's are a LexicalScoreThreshold and a reputation-feed allowlist. A single Sysmon EventID 22 record carries QueryName, QueryStatus and Image, but 'this one query failed' is not the technique — the technique is the failure rate and the randomness of the string, neither of which a per-event Sigma selection can compute. […]
Covered instead by T1568, T1568.001, T1568.003, T1071.004, T1008.
What the technique is
Adversaries may make use of Domain Generation Algorithms (DGAs) to dynamically identify a destination domain for command and control traffic rather than relying on a list of static IP addresses or domains. This has the advantage of making it much harder for defenders to block, track, or take over the command and control channel, as there potentially could be thousands of domains that malware can check for instructions. DGAs can take the form of apparently random or “gibberish” strings (ex: istgmxdejdnxuyla.ru) when they construct domain names by generating each letter. Alternatively, some DGAs employ whole words as the unit by concatenating words together instead of letters (ex: cityjulydish.net). Many DGAs are time-based, generating a different domain for each time period (hourly, daily, monthly, etc). Others incorporate a seed value as well to make predicting future domains more difficult for defenders. Adversaries may use DGAs for the purpose of Fallback Channels. When contact is lost with the primary command and control server malware may employ a DGA as a means to reestablishing command and control.
Read it on attack.mitre.orgWhat MITRE says you would watch
- AN1178
Correlate DNS queries that generate domains with high entropy or gibberish patterns, combined with short-lived connections from unusual processes. Monitor Sysmon DNS events and Windows Security logs for abnormal query rates and failed lookups.
- AN1179
Identify processes issuing repeated DNS queries to random-looking domains with abnormal entropy or word concatenations. Correlate resolver logs with high NXDOMAIN rates and auditd socket connections.
- AN1180
Monitor unified DNS logs for abnormal domain queries with low lexical similarity to known domains, repeated failed lookups, and random string structures. Cross-check with process logs to confirm unusual origins (non-browser apps).
Technique names and descriptions © MITRE ATT&CK®, CC BY 4.0. Not endorsed by MITRE.