T1595.003Not expressible in Sigma

Wordlist Scanning

ReconnaissancePRE

Where this stands

No Sigma rule can address this — the telemetry MITRE names has no Sigma logsource behind it.

This happens on infrastructure you do not own, so it never reaches your logs. MITRE's own guidance is internet scanning and threat intelligence, not log analysis.

What the technique is

Adversaries may iteratively probe infrastructure using brute-forcing and crawling techniques. While this technique employs similar methods to Brute Force, its goal is the identification of content and infrastructure rather than the discovery of valid credentials. Wordlists used in these scans may contain generic, commonly used names and file extensions or terms specific to a particular software. Adversaries may also create custom, target-specific wordlists using data gathered from other Reconnaissance techniques (ex: Gather Victim Org Information, or Search Victim-Owned Websites). For example, adversaries may use web content discovery tools such as Dirb, DirBuster, and GoBuster and generic or custom wordlists to enumerate a website’s pages and directories. This can help them to discover old, vulnerable pages or hidden administrative portals that could become the target of further operations (ex: Exploit Public-Facing Application or Brute Force). As cloud storage solutions typically use globally unique names, adversaries may also use target-specific wordlists and tools such as s3recon and GCPBucketBrute to enumerate public and private buckets on cloud infrastructure. Once storage objects are discovered, adversaries may leverage Data from Cloud Storage to access valuable information that can be exfiltrated or used to escalate privileges and move laterally.

Read it on attack.mitre.org

What MITRE says you would watch

AN2000
Monitor for suspicious network traffic that could be indicative of scanning, such as large quantities originating from a single source (especially if the source is known to be associated with an adversary/botnet).