Detect Domain Generation Algorithms in IBM QRadar
Adversaries use Domain Generation Algorithms (DGAs) to dynamically identify C2 destinations by algorithmically generating large numbers of candidate domain names. Only the operator-registered domain resolves successfully; all others return NXDOMAIN. This makes blocking impractical — defenders cannot predict the full space of generated domains. DGAs may produce random character strings (e.g., istgmxdejdnxuyla.ru) or concatenate dictionary words (e.g., cityjulydish.net). Many implementations are time-seeded, generating different candidate domains hourly or daily. Some incorporate a shared secret seed to prevent defender prediction. Detection focuses on statistical anomalies: abnormally high NXDOMAIN failure rates from a single host, domain names with low vowel ratios or high character entropy, rapid successive queries to many unique failing domains, and beaconing patterns once a DGA domain resolves. Malware families using DGA include QakBot, Conficker, Ursnif, DarkWatchman, BONDUPDATER, POSHSPY, CHOPSTICK, Aria-body, Milan, SombRAT, and MiniDuke. APT41 changes C2 monthly via DGA; TA551 generates URLs from executed macros.
MITRE ATT&CK
- Tactic
- Command and Control
- Technique
- T1568 Dynamic Resolution
- Sub-technique
- T1568.002 Domain Generation Algorithms
- Canonical reference
- https://attack.mitre.org/techniques/T1568/002/
QRadar Detection Query
SELECT
sourceip,
"hostname",
COUNT(*) AS total_nxdomain,
COUNT(DISTINCT "dns_query_name") AS unique_nx_domains,
SUM(CASE WHEN
/* Vowel ratio < 20% heuristic via low vowel character presence */
(CHAR_LENGTH(REGEXP_REPLACE(LOWER("sld_label"), '[^aeiou]', '')) * 1.0 /
NULLIF(CHAR_LENGTH("sld_label"), 0)) < 0.20
OR
/* Digit ratio > 35% */
(CHAR_LENGTH(REGEXP_REPLACE("sld_label", '[^0-9]', '')) * 1.0 /
NULLIF(CHAR_LENGTH("sld_label"), 0)) > 0.35
OR
/* Abnormally long SLD */
CHAR_LENGTH("sld_label") > 16
THEN 1 ELSE 0 END) AS likely_dga_count,
MIN(starttime) AS first_seen,
MAX(starttime) AS last_seen
FROM (
SELECT
sourceip,
"hostname",
starttime,
"dns_query_name",
LOWER(
REGEXP_REPLACE(
REGEXP_REPLACE("dns_query_name", '^(.+\.)?([^.]+)\.[^.]+$', '\\2'),
' ', ''
)
) AS "sld_label"
FROM events
WHERE
LOGSOURCETYPEID IN (SELECT id FROM logsourcetypes WHERE name ILIKE '%DNS%')
AND QIDNAME(qid) ILIKE '%NXDOMAIN%'
AND starttime > NOW() - 3600000
AND "dns_query_name" IS NOT NULL
AND CHAR_LENGTH("dns_query_name") > 0
) subq
WHERE CHAR_LENGTH("sld_label") >= 7
GROUP BY sourceip, "hostname"
HAVING total_nxdomain >= 20
AND unique_nx_domains >= 15
ORDER BY likely_dga_count DESC, total_nxdomain DESCDetects hosts generating suspicious volumes of NXDOMAIN DNS failures indicative of DGA C2 activity. Queries DNS log sources in QRadar for NXDOMAIN events, extracts the second-level domain (SLD), applies vowel ratio, digit ratio, and length heuristics to flag likely algorithmically-generated domains, and alerts when a host exceeds both the total failure count and unique domain thresholds within a rolling 1-hour window.
Data Sources
Required Tables
False Positives & Tuning
- Internal DNS resolvers aggregated behind a single source IP will appear to generate high NXDOMAIN rates from one host even though the traffic originates from many endpoints
- Software update services with aggressive retry logic querying CDN endpoints that have changed DNS records will generate NXDOMAIN bursts
- Penetration testing or vulnerability scanning tools executing DNS brute-force enumeration of subdomains against target domains
Other platforms for T1568.002
Testing Methodology
Validate this detection against 4 adversary techniques from Atomic Red Team. Each test below lists the behaviour to exercise and the telemetry you should expect to see. Executable commands and cleanup steps are available with Pro.
- Test 1PowerShell Time-Seeded DGA Simulation (Conficker-Style)
Expected signal: Sysmon Event ID 22 (DNS Query): 30 entries with Image=powershell.exe, QueryName values containing random-character strings (10-16 chars, low vowel ratio). QueryStatus will show 'No Such Name' or equivalent NXDOMAIN code for all 30. DnsEvents: ResultCode=3 for all generated domains. The Sysmon process chain shows powershell.exe as the Image with no suspicious parent.
- Test 2Bash DGA Simulation — Random Character String Domains (Linux/macOS)
Expected signal: Linux auditd SYSCALL records for nslookup execution with random domain arguments (if auditd configured for execve syscalls). Syslog entries from nslookup showing NXDOMAIN responses. Network capture shows UDP port 53 queries to the configured resolver for random-string .com domains. EDR process telemetry: nslookup spawned 30 times from bash with unique arguments per invocation.
- Test 3Python DGA Simulation with Date-Seeded Algorithm
Expected signal: Sysmon Event ID 1: python3.exe process creation with command line containing the DGA script inline. Sysmon Event ID 22: 30 DNS query events with Image=python3.exe (or python.exe), QueryName values showing random lowercase strings ending in .net. Windows Security Event 4688 (if command line auditing enabled) shows the full python3.exe invocation.
- Test 4Rapid nslookup Batch — High-Entropy Domain Names (Windows CMD)
Expected signal: Sysmon Event ID 22: 17 DNS query events with Image=nslookup.exe (or cmd.exe as parent), each QueryName showing a consonant-heavy random string ending in .com. All return NXDOMAIN. Windows Security Event 4688 shows cmd.exe execution followed by multiple nslookup.exe child processes. The batch executes in approximately 2-5 seconds, creating a high-velocity NXDOMAIN burst.
References (12)
- https://attack.mitre.org/techniques/T1568/002/
- https://umbrella.cisco.com/blog/2016/10/10/domain-generation-algorithms-effective/
- http://go.cybereason.com/rs/996-YZT-709/images/Cybereason-Lab-Analysis-Dissecting-DGAs-Eight-Real-World-DGA-Variants.pdf
- https://unit42.paloaltonetworks.com/threat-brief-understanding-domain-generation-algorithms-dga/
- https://arxiv.org/pdf/1611.00791.pdf
- https://datadrivensecurity.info/blog/posts/2014/Oct/dga-part2/
- https://www.welivesecurity.com/2017/12/21/sednit-update-fancy-bear-spent-year/
- https://www.fireeye.com/blog/threat-research/2017/03/dissecting_one_ofap.html
- http://blog.talosintelligence.com/2017/09/avast-distributes-malware.html
- https://learn.microsoft.com/en-us/azure/sentinel/dns-domain-generation-algorithm
- https://docs.microsoft.com/en-us/sysinternals/downloads/sysmon
- https://github.com/redcanaryco/atomic-red-team/blob/master/atomics/T1568.002/T1568.002.md
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