Does "no alert" really mean "no incident"?
No. "No alert" means only that nothing matched the detection rules your SIEM happens to have. On average, those rules cover just 21% of the techniques attackers actually use — so the absence of an alert says far less about your safety than most teams assume.
Published June 8, 2026 · ~9 min read · By Achim Kraus, CTO
The most dangerous assumption in security
The console is green. Logs are flowing. No alerts. And yet the quiet question before every audit: are we sure? "No alert" gets read as "no incident." It is the most dangerous silent assumption in a security program — and the reason has nothing to do with a SIEM vendor failing.
What the numbers actually say
Across hundreds of production SIEMs — Splunk, Sentinel, QRadar, CrowdStrike LogScale, Google SecOps — the average coverage of known attacker techniques is just 21%.
Source: CardinalOps, 5th Annual State of SIEM Detection Risk, 2025.
- Enterprise SIEMs cover an average of 21% of MITRE ATT&CK techniques — 79% remain undetected. (CardinalOps, 5th Annual State of SIEM Detection Risk, 2025.)
- Across the top ten techniques observed in real-world attacks, organizations cover only four.
- 13% of existing detection rules are non-functional — broken by misconfigured data sources or missing log fields.
- 90% of organizations already ingest enough data to potentially cover ~90% of techniques. Data is not the bottleneck; detection logic is.
The study analyzed the largest SIEM sample on record: more than 13,000 detection rules, 2.5 million log sources, and hundreds of production deployments across Splunk, Microsoft Sentinel, IBM QRadar, CrowdStrike Falcon LogScale, and Google SecOps.
Why the gap exists — and why it is not a SIEM failure
A SIEM is indispensable. It is also structurally incapable of auditing itself. Five reasons the 79% gap is normal, not negligent:
Detection rules are written and maintained by humans
Full coverage of a moving target like MITRE ATT&CK is economically out of reach for any in-house team.
What is not logged or onboarded cannot be detected
Every missed data source is an invisible blind spot the SIEM cannot warn you about.
Rule-based logic misses behavioral anomalies
Activity that does not match a known pattern slips through — including most credential-based intrusions.
Alert fatigue buries real detections
Genuine signals disappear in the noise of triage queues, even when the rule did fire.
Configuration drift
Rules age, environments change — which is exactly why CardinalOps finds 13% of rules already broken.
The attacks that leave no signature
CrowdStrike reports that 81% of intrusions between July 2024 and June 2025 were malware-free — adversaries logged in with valid credentials, moved laterally, and lived off the land. Activity like this rarely triggers a signature-based alert.
But it does leave traces — in the network. Unusual lateral connections. New external destinations. Atypical volumes. Connections at hours that do not match the asset's normal behavior. The signal is there; the question is whether anyone is looking on a layer that does not depend on what the attacker chose to log.
Turning the question around
A SIEM asks: "Does anything here match one of my detection patterns?"
An independent network view asks a different question: "What is actually happening here — and does it match what should be happening?"
The second question finds activity that does not trigger a known pattern. It does not depend on which log sources happen to be onboarded. And it is immune to alert fatigue, because it is read periodically or continuously rather than firing in real time. It does not replace a SIEM. It answers a question the SIEM cannot answer about itself.
See, do not react. An independent view answers the question — it does not replace incident response, EDR, or your existing controls. Its job is to tell you whether the green console matches reality.
NDR as a second, independent view
Network Detection and Response (NDR) is the category that provides this view: continuous, log-independent, working on connection and behavioral evidence. Industry analysts place the MITRE/SIEM coverage gap precisely where NDR provides visibility that does not depend on logs or predefined rules.
AEGYS Monitor is that second, independent view. Not a SIEM replacement — a reality check. Useful before an audit, after a suspected incident, during M&A, or as a continuous baseline that answers the one question a SIEM cannot answer about itself: is anything happening here that we are not seeing?
15 minutes. No sales pitch.
Take-away in three lines
- "No alert" does not mean "no incident." It means nothing matched the rules you currently have.
- The 79% gap is structural — manual rule maintenance, log onboarding, rule logic, alert load, configuration drift.
- To answer "is anything actually happening?" you need a second, independent view — not a second SIEM.
Related reading: Vulnerability scan vs. penetration test vs. automated security validation — the proof side of the same coin. And AEGYS Monitor as a SIEM alternative for teams without the appetite for a multi-month SIEM project.