Topic starter
02/08/2026 11:38 am
TL;DR: Legacy SIEMs often appear healthy while silently dropping critical telemetry, leaving investigations without authentication, firewall, or workload evidence when incidents begin, according to DataBahn. The real problem is governance of data coverage, not just log volume, because blind spots and low-value ingestion both undermine detection and response.
Editorial analysis by NHI Mgmt Group, based on content published by DataBahn: “Are We Collecting the Right Data? Log Source Coverage and Data Visibility”.
Key questions
Q: What fails when a SIEM has ingestion but no coverage assurance?
A: The failure is not the platform’s ability to ingest data, but the organisation’s ability to prove the right sources are still sending the right events.
Q: Why do missing authentication or firewall logs create such a large investigation risk?
A: Authentication and firewall logs often provide the first reliable reconstruction of who accessed what, from where, and when.
Q: How do security teams know if SIEM coverage is actually working?
A: They verify the path from source to rule, not just the rule itself.
Practitioner guidance
- Establish a live log source inventory Catalog every critical source with owner, business unit, log type, expected frequency, and downstream destination so missing telemetry is visible before an incident exposes it.
- Classify sources by investigative value Separate authentication, firewall, workload, and privileged infrastructure logs from low-value noise so ingestion decisions are based on evidence value, not raw volume.
- Monitor source health continuously Alert on silent, whispering, and noisy sources so degradations are detected within minutes rather than during an investigation.
Bottom line: Legacy SIEMs can appear healthy while silently losing the logs that investigations depend on most.
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02/08/2026 12:51 pm
Coverage assurance is now a governance control, not a housekeeping task. If teams cannot tell which critical sources are healthy, silent, or never onboarded, they do not have a reliable security record of the environment. The problem is amplified in identity-heavy estates because service accounts, authentication systems, and privileged infrastructure often produce the very evidence needed for investigations. Practitioners should treat telemetry completeness as part of security governance, not a back-office logging concern.
A few things that frame the scale:
- Only 5.7% of organisations have full visibility into their service accounts, according to the Ultimate Guide to NHIs.
- By 2029, 40% of enterprises that successfully implement zero trust within cloud service provider environments will rely on the advanced visibility and control capabilities offered by CNAPP solutions.
A question worth separating out:
Q: Should teams prioritise reducing noisy logs or fixing silent sources first?
A: Fix silent sources first, because missing evidence creates direct investigation risk while noisy logs mainly create cost and analyst fatigue. Once critical sources are reliable, teams can tune low-value ingestion without weakening the telemetry needed for detection and forensics.
👉 Read our full editorial: Legacy SIEM data coverage gaps are the hidden investigation failure