Proving that individuals who access Controlled Unclassified Information (CUI) or sensitive contractor systems are properly identified is a foundational requirement of FAR 52.204-21 and CMMC 2.0 Level 1 (IA.L1-B.1.V); the practical way to demonstrate this to auditors is with authoritative system logs and a SIEM that collects, normalizes, and preserves authentication events as verifiable evidence.
What to log to prove identification — practical implementation for the Compliance Framework
Start by defining the minimum set of authentication-related events your Compliance Framework practice requires: successful and failed logons, account creations, privilege changes, password resets, MFA challenge results, and account disablements. Technical sources include Windows Security Event Log (Event ID 4624 for successful logon, 4625 for failed logon, 4720 for user creation), Linux /var/log/auth.log or systemd journal (e.g., "sshd: Accepted publickey for
SIEM configuration and building audit-ready evidence
In the SIEM, normalize fields (user.name, user.id, event.type, event.outcome, source.ip, src.port, host.name, @timestamp) so queries return consistent results regardless of source. Create saved searches and dashboards that can produce an auditor-ready report for a given username and date range. Example actionable queries: event.type:authentication AND user.name:"jdoe" AND @timestamp:[2026-04-01 TO 2026-04-12] (Elastic) or an equivalent KQL for Microsoft Sentinel. Implement parsers to extract MFA results (success/failure) and correlate sign-in with MFA logs to show the authentication chain. When exporting evidence, produce immutable exports (compressed JSON/CSV) and generate a SHA-256 hash for each export; store the export + hash in a tamper-evident location (write-once S3 or an archived share) and include the hash in your evidence package. Record chain-of-custody metadata: who ran the export, when, and why.
Small business scenario: step-by-step example
Scenario — a 25-person engineering subcontractor using Office 365 (Azure AD) for identity and a small on-prem AD domain plus two Linux app servers: To prove identification for an engineer "alice.smith", gather: (1) Azure AD Sign-in log showing successful interactive sign-in and conditional access/MFA result with timestamp and client IP; (2) AD security event 4624 on the domain controller showing the local session; (3) syslog entry from the app server showing SSH publickey acceptance for alice.smith from the same client IP or the corporate VPN IP; (4) ticket from the helpdesk workflow showing account provisioning and approval. In the SIEM, correlate these four items by timestamp and user.name, export the correlation view to PDF/JSON, generate a SHA-256 digest, and include the original log snippets (with event IDs). This combined package demonstrates the identity, authentication method (MFA/keys), approval process, and timeline — exactly the evidence an auditor will seek under Compliance Framework practices.
Configuration details and technical best practices
Technical items small businesses often miss but must implement: (1) Time synchronization — configure NTP (or platform-managed time) across domain controllers, servers, network devices and SIEM collectors to within a few seconds to enable reliable correlation; (2) Agent selection — use Beats/NXLog for structured collection to preserve original fields and event IDs; (3) Preservation — retain raw logs for a minimum practical window (recommendation: 90 days online, 1 year archived/accessible) and document retention policy in your compliance artifacts; (4) Log integrity — enable signed log forwarding where supported or store ingested logs in an append-only repository; (5) Access controls — restrict who can query/export SIEM data and log all SIEM admin actions so the evidence trail itself is auditable.
Risk of not implementing logs and SIEM correctly
Without consistent logging and SIEM correlation you risk being unable to prove who accessed systems or CUI, leading to failed FAR 52.204-21 / CMMC reviews, loss of contracts, or missed breach detection. Operationally, poor logging hinders incident response (you cannot trace lateral movement or scope a compromise), increases dwell time for attackers, and results in ineffective access reviews. For small businesses, the reputational and contractual consequences of being unable to demonstrate identification controls are often more damaging than the cost of implementing basic logging and SIEM capabilities.
Compliance tips and practical checklist
Actionable checklist: 1) Map identity sources and ensure all are forwarding relevant auth logs to SIEM; 2) Standardize log formats and field names; 3) Enable and retain MFA logs and conditional access details; 4) Document the process for producing an auditor packet (queries, export steps, hashing, who approves); 5) Run quarterly exercises: produce an evidence packet for three random users and review with internal compliance; 6) Maintain an identity lifecycle record (onboard/offboard tickets) to pair with logs; 7) Budget for any cloud license needed to retain sign-in logs beyond default windows (e.g., Azure AD retention); 8) Use correlation rules for anomalies (impossible travel, multiple failed logons, new device logins) and tune to reduce noise. These steps align with Compliance Framework expectations for demonstrable, repeatable evidence.
In summary, proving identification for FAR 52.204-21 and CMMC 2.0 Level 1 is largely a discipline of generating the right logs, centralizing them in a SIEM, normalizing and correlating identity events, and packaging those findings in a tamper-evident way for auditors. For small businesses, focus on high-impact items first — centralize auth logs, enable MFA logging, synchronize time, and create a documented, repeatable evidence export procedure — and you will cover the majority of the Compliance Framework requirements efficiently and defensibly.
