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Upgrade to ProDetect DNS Subdomain Wordlist Brute-Force Enumeration in Google Chronicle
Adversaries iteratively query an organization's authoritative or recursive DNS infrastructure with large wordlists of candidate subdomain labels (dev, staging, vpn, mail-old, api-internal, etc.) to discover hostnames that were never intentionally published — forgotten staging environments, internal-only services accidentally exposed, or third-party integrations. Unlike the HTTP directory/file wordlist scanning covered by generic Active Scanning detections, this technique operates entirely at the DNS layer using tools such as massdns, puredns, gobuster's dns mode, dnsrecon, fierce, and amass's active enumeration mode, which resolve thousands of candidate FQDNs per minute and rely on the high NXDOMAIN response rate as an intrinsic side effect of brute-forcing an unknown namespace. Because these queries never touch a web server or generate an HTTP log line, they are invisible to WAF- and web-access-log-based scanning detections and require dedicated visibility into DNS server query logs (authoritative nameserver, recursive resolver, or DNS security gateway) plus endpoint process telemetry for internal pivot scanning.
MITRE ATT&CK
- Tactic
- Reconnaissance
YARA-L Detection Query
rule dns_subdomain_wordlist_enumeration {
meta:
author = "df00tech Detection Engineering"
description = "Detects host-level indicators of DNS subdomain wordlist brute-forcing: execution of named DNS enumeration tools"
severity = "MEDIUM"
mitre_attack_tactic = "Reconnaissance"
mitre_attack_technique = "T1595.003"
created = "2026-07-21"
events:
$e.metadata.event_type = "PROCESS_LAUNCH"
re.regex($e.target.process.file.full_path, `(?i)(massdns|gobuster|puredns|dnsrecon|fierce|amass|dnsx|altdns)`)
condition:
$e
}Chronicle YARA-L 2.0 rule matching PROCESS_LAUNCH UDM events for execution of named DNS subdomain enumeration tools (massdns, gobuster, puredns, dnsrecon, fierce, amass, dnsx, altdns). This detects the host-visible precursor/pivot signal; correlate with NETWORK_DNS UDM events showing a high NXDOMAIN ratio from the same source for full-chain confirmation of an active subdomain brute-force campaign.
Data Sources
Required Tables
False Positives & Tuning
- Security engineering or ASM teams running authorized subdomain discovery tooling for attack-surface inventory
- Approved red team engagements actively enumerating the DNS namespace
Other platforms for THREAT-Recon-DNSSubdomainWordlistEnumeration
Testing Methodology
Validate this detection against 3 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 1Simulated DNS Subdomain Wordlist Query Burst
Expected signal: Authoritative/recursive DNS server query log entries showing 60 sequential NXDOMAIN responses for distinct subdomains of example.com from the executing host's source IP within a short window.
- Test 2gobuster DNS Mode Execution
Expected signal: Process creation event for gobuster with CommandLine containing 'dns -d example.com -w' and the wordlist file path.
- Test 3massdns Bulk Subdomain Resolution
Expected signal: Process creation event for massdns with CommandLine containing '-r' and '-t A' flags; DNS query log entries for the listed candidate subdomains.
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