Seumas Jarrett
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With OAuth 2.0 Device Code Flow phishing campaigns actively targeting M365 environments in financial services and beyond, I built a cross-phase KQL detection rule that moves beyond the obvious deviceCode protocol filter — because the real damage happens in tables most hunts never look at.
The rule correlates three phases across both SigninLogs and AADNonInteractiveUserSignInLogs:
Phase 1 catches victim-side device code authentications, filtering out primaryRefreshToken (enrolled devices) and known low-risk resources to cut noise at the source.
Phase 2 surfaces non-interactive single-factor token replay activity — this is where the attacker's stolen OAuth token actually appears, silently blending into background API traffic.
Phase 3 identifies post-compromise Graph/mail resource access across anomalous IP counts — the data exfiltration and BEC staging layer.
The key design decisions that make it production-ready: a cross-phase inner join so only users appearing in Phase 1 and Phase 2 surface at all, a MinutesToReplay temporal constraint (>= 0 and <= 2880) to eliminate false correlations where phases are coincidental rather than causal, and a composite risk score with banded severity output.
Tested against 90 days of real tenant data. Came back clean after tuning — which is the outcome you want before deploying as a scheduled analytics rule.
The rule correlates three phases across both SigninLogs and AADNonInteractiveUserSignInLogs:
Phase 1 catches victim-side device code authentications, filtering out primaryRefreshToken (enrolled devices) and known low-risk resources to cut noise at the source.
Phase 2 surfaces non-interactive single-factor token replay activity — this is where the attacker's stolen OAuth token actually appears, silently blending into background API traffic.
Phase 3 identifies post-compromise Graph/mail resource access across anomalous IP counts — the data exfiltration and BEC staging layer.
The key design decisions that make it production-ready: a cross-phase inner join so only users appearing in Phase 1 and Phase 2 surface at all, a MinutesToReplay temporal constraint (>= 0 and <= 2880) to eliminate false correlations where phases are coincidental rather than causal, and a composite risk score with banded severity output.
Tested against 90 days of real tenant data. Came back clean after tuning — which is the outcome you want before deploying as a scheduled analytics rule.
