Understanding the Full Spectrum of Threat Indicators
Cybersec Café #75 - 07/08/25
If you’ve spent more than a day in cybersecurity, you’ve definitely heard the phrase Indicators of Compromise, or IOCs, thrown around.
It’s often used as a blanket term for signals or behaviors that point to a potential threat, but it really only scratches the surface.
Threat indicators span a broader spectrum. Some are technical - concrete data points that may signal an attack or breach. While others are behavioral - suspicious activity or patterns that suggest something might be off.
By understanding the various terms and associated indicators, you can leverage them to sharpen your detections, improve your monitoring strategy, and proactively harden your defenses. They can also play a key role in shaping incident response plans by helping build processes tailored to the threats specific to your environment.
Not to mention, they’ll help you communicate clearly to your team members.
Put simply: knowing the full range of threat indicators means spotting and stopping threats before they escalate into something bigger.
While some of the terms we’ll cover are formal cybersecurity lingo, others are more contextual and used flexibly depending on the team or environment. I’ll highlight both, along with any alternate terminology you may hear.
Indicators of Compromise (IOC)
Indicators of Compromise observable pieces of evidence showing that a system or network has been breached. These typically surface during forensics work or investigations and act as proof that an attack has succeeded. Examples include known malicious IP addresses, malware hashes, or traces of unauthorized activity.
Alternate Terminology: Forensics, Artifacts, Evidence
Indicators of Attack (IOA)
Indicators of Attack signal that an attack is underway, even if an attacker hasn’t fully compromised systems yet. These clues often come from SIEM alerts, threat hunts, or patterns in logs that point to malicious activity in progress, like DoS attempts or suspicious process creations. Some common examples include command injection attempts, known malicious patterns in logs, or blocked lateral movement.
Alternate Terminology: Attack Activity, Attack Patterns
Indicators of Fraud
Indicators of Fraud point to social engineering, potential financial fraud, or account abuse - often surfacing as behavioral threat indicators. They can take many forms, from multiple failed payment attempts to phishing campaigns or signs of account takeovers. These indicators help teams spot and respond to abuse before significant damage occurs.
Alternate Terminology: Fraud Signals, Fraud Markers
Indicators of Misconfiguration (IOM)
Indicators of Misconfiguration are signs that systems or controls have been set up incorrectly. These can show up across your entire stack, but are especially common in cloud environments, infrastructure-as-code, and weak internal processes. Think open S3 buckets, overly permissive firewall rules, excessive user permissions, or default administrator credentials left unchanged.
Alternate Terminology: Misconfiguration Findings, Configuration Weaknesses
Indicators of Exposure
Indicators of Exposure are signs that sensitive data or infrastructure is publicly accessible or discoverable by attackers. They often live in plain sight and can be difficult to track. Sometimes on the surface web, sometimes leaked on the dark web. Examples include leaked credentials, exposed developer databases, open services found via Shodan, or code repositories containing hardcoded secrets.
Alternate Terminology: Exposure Signals, Public Data Leakage
Indicators of Behavior (IOB)
Indicators of Behavior are anomalies in either user or system activity that may suggest malicious intent or policy violations. While powerful, behavior-based indicators are notoriously finicky and often require human investigation due to high potential for false positives. Examples include impossible travel logins, unusual access patterns, abnormal working hours, or signs of automated user behavior.
Alternate Terminology: User Behavior Analytics, Entity Behavior Signals
Indicators of Vulnerability
Indicators of vulnerability are details about known weaknesses in systems that attackers could exploit. These can typically be rectified through regular patching, updates, or configuration changes. Examples include CVEs, deprecated software versions, and vulnerability scan results.
Alternate Terminology: Vulnerability Findings
Indicators of Reconnaissance (IOR)
Indicators of Reconnaissance are signs that an attacker is gathering information about your environment, likely before attempting an attack. While they can be more difficult to mitigate if they’re targeting your external attack surface, they’re often detectable due to their automated nature. Examples include network scans, DNS enumeration, OSINT collection of employee details, or social engineering efforts.
Alternate Terminology: Recon Activity
Indicators of Insider Threat
Indicators of Insider Threat are signs of malicious or risky actions by legitimate users within your organization. Insider threats can be particularly challenging to detect, but careful behavioral analysis can reveal warning signs. Examples include mass downloads of sensitive data, unusual privilege escalation, policy violations, or acts of sabotage.
Alternate Terminology: Insider Risk Signals, Trusted User Abuse Indicators
Indicators of Command and Control
Indicators of Command and Control reveal that a compromised system is communicating with attacker-controlled infrastructure. Detecting C2 activity relies heavily on monitoring network traffic, DNS queries, and identifying suspicious communication patterns. Examples include unusual protocol usage, beaconing to known C2 domains, regular timed outbound connections, or malware callbacks.
Alternate Terminology: C2, Beacon
Indicators of Data Exfiltration
Indicators of Data Exfiltration are signs that sensitive data is being stolen or transferred out of your network. Security teams should invest in robust Data Loss Prevention strategies to detect and stop exfiltration attempts. Examples include DLP alerts, unusually large outbound file transfers, excessive file downloads, or encrypted outbound channels designed to evade monitoring.
Alternate Terminology: Data Loss Signals, Exfil
Whether it’s Detection Engineering, Incident Response, or Threat Huting - Security Operations is built on data. And as a Security Engineer, you need to make that data work for you. Selecty is a database-agnostic, sidecar query assistant built to do just that. Generate queries based on your table schehmas, optimize them to your use case, iterate on them quickly, and debug faster than ever - all in one sleek interface. Check it out!
Why it’s Important to Think Beyond IOCs
While Indicators of Compromise are undeniably valuable in detecting and responding to known threats, they’re inherently reactive and limited in scope.
Attackers know this, and they continuously evolve their tactics to bypass detection strategies that rely solely on static IOCs.
Expanding your perspective to the full spectrum of threat indicators allows you and your team to move beyond chasing known patterns. It pushes you to consider the broader context of suspicious activity, misconfigurations, exposure, and behavioral anomalies in your environment.
Regularly thinking about these different types of threat indicators helps you:
Build a detection suite with broader and more complete coverage.
Threat hunt with greater purpose and direction.
Expand your forensic scope during incident response to capture the true impact.
Embracing these threat indicators proactively doesn’t just strengthen your security posture, it helps you truly understand your attack surface and better anticipate the constantly shifting threat landscape.
Securely Yours,
Ryan G. Cox
P.S. The Cybersec Cafe follows a weekly cadence.
Each week, I deliver a Deep Dive on a cybersecurity topic designed to sharpen your perspective, strengthen your technical edge, and support your growth as a professional - straight to your inbox.
. . .
For more insights and updates between issues, you can always find me on Twitter/X or my Website. Let’s keep learning, sharing, and leveling up together.