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Upgrade to ProDetect Automated Vulnerability Scanner Sweep Against External Attack Surface in Google Chronicle
Before exploitation, most intrusions begin with active scanning of the target's external attack surface using automated vulnerability scanning tools such as sqlmap, Nikto, Nuclei, Acunetix, Nessus, OpenVAS, or WPScan. Attackers run these tools against internet-facing web applications, APIs, and edge devices to fingerprint software versions, enumerate misconfigurations, and identify exploitable CVEs before committing to an intrusion attempt. This scanning is typically noisy at the HTTP layer: high-volume requests for known vulnerable paths (e.g. /.env, /.git/config, /wp-login.php, /actuator/health, /phpmyadmin), distinctive scanner user-agent strings, and rapid sequential probing of many distinct URIs from a single source in a short window. Nation-state actors such as Volt Typhoon and APT41 routinely scan edge devices and web infrastructure ahead of exploitation attempts, while eCrime groups like FIN7 and Scattered Spider use commodity scanning frameworks to identify soft targets at scale. Detecting the scanning phase gives defenders a window to harden or patch before the attacker moves to Initial Access.
MITRE ATT&CK
- Tactic
- Reconnaissance
YARA-L Detection Query
rule automated_vuln_scanner_sweep {
meta:
author = "df00tech"
description = "Detects automated vulnerability scanner tool signatures and sensitive path probing against WAF-protected web infrastructure"
severity = "MEDIUM"
priority = "MEDIUM"
mitre_attack_tactic = "Reconnaissance"
mitre_attack_technique = "T1595.002"
version = "1.0"
events:
$req.metadata.event_type = "NETWORK_HTTP"
$req.target.application = /(?i)(f5|imperva|fortiweb|akamai|cloudflare|netscaler)/
(
$req.network.http.user_agent = /(?i)(sqlmap|nikto|nuclei|acunetix|nessus|openvas|wpscan|dirbuster|gobuster)/
OR $req.target.url = /(?i)(\.env|\.git\/config|wp-login\.php|actuator\/env|phpmyadmin|\.aws\/credentials)/
)
$req.principal.ip = $src_ip
match:
$src_ip over 5m
outcome:
$request_count = count_distinct($req.metadata.id)
$distinct_uris = count_distinct($req.target.url)
$sample_uris = array_distinct($req.target.url)
condition:
#req >= 1
}YARA-L 2.0 rule for Google Chronicle SIEM detecting known vulnerability scanner user-agent strings or sensitive-path requests against WAF-protected HTTP infrastructure within a 5-minute window.
Data Sources
Required Tables
False Positives & Tuning
- Authorised vulnerability management scans not yet excluded via allowlist
- Bug bounty or authorised penetration testing traffic
- Synthetic monitoring tools with unusual but benign user-agent strings
Other platforms for THREAT-Recon-AutomatedVulnScannerSweep
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 1Vulnerability Scanner User-Agent Simulation via curl
Expected signal: WAF/reverse-proxy logs record inbound requests with the scanner user-agent strings in the Message or http_user_agent field.
- Test 2Sensitive Path Probing Simulation
Expected signal: WAF/reverse-proxy logs show requests to each sensitive path, mostly resulting in 404 responses.
- Test 3Behavioral URI Enumeration Simulation via ffuf-style Loop
Expected signal: WAF/reverse-proxy logs record 40 distinct URIs requested from the test source IP within a single 5-minute window, nearly all returning 404.
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Related Detections
Tactic Hub
Detection Variants (2)
Different telemetry and tradecraft for the same technique — pick the one that matches the data you collect.
- THREAT-Recon-DistributedVulnScanBurstDistributed Vulnerability Scanning Burst Against Web Infrastructure
- THREAT-Recon-ExternalVulnScannerBurstDetectionExternal Vulnerability Scanner Burst/Sweep Against Internet-Facing AssetsBurst/sweep rate-and-breadth angle on external, internet-facing vulnerability scanning — distinct from the tool-signature and internal-scanner-execution branches already covered on the T1595.002 technique page; this detection fires purely on request volume/uniqueness from a single external source against WAF/firewall/proxy logs, without relying on scanner tool names or user-agent strings.