Incident: Failed logon burst followed by successful authentication (+1 related finding)

Case: CASE-001
Generated: 2026-09-26 11:08:02 UTC
Status: complete
Severity: CRITICAL
Grouping confidence: medium (how strongly findings are linked, not whether an intrusion occurred)
Hosts: WS-3250, WS-7003
Accounts: acct-8592
Window: 2026-08-01 08:00:00 -> 08:06:00 UTC (360s)
Telemetry: generated_auth_execution

This report was produced by an automated investigation. It presents evidence-backed findings for analyst review and does not authorise or perform any response action.

Verdict

Disposition: Malicious
Decided by: deterministic triage of the seed findings
Engine: deterministic
Profile: operational-v6
Model: none (deterministic engine)
Evidence basis: 28 typed observation(s) checked against recorded telemetry; 0 claim(s) rejected by verification; 3 specialist step(s) run (endpoint, identity, attack); 8 tool call(s) served, 0 refused.
Supporting event ids: none cited by the concluding explanations

This system does not compute a confidence score for its verdict. The evidence basis is a count of what was checked, not a measure of how likely the verdict is.

Investigation Tree

Initial alert: Failed logon burst followed by successful authentication (+1 related finding)
rules ATH-005, ATH-007; 14 seed event(s): 1f776b2d12b6e1b38138, 4b7981dfd851184e370d, 7ae112de50a7ef35212b, 80fa003ab0d4b9fb50d3, 880b1242f36a26407c74, 8e3b9127b110d0908581, +8 more
↓
ATH investigation (engine deterministic)
- endpoint
  why deterministic priority order; case evidence rests on process_command_line, process_execution, process_lineage telemetry (from ATH-007)
  tools get_events, get_events, process_tree
  new events 1 retrieved; shown: 21cfbf2f84aba973509b
- identity
  why deterministic priority order; case evidence rests on auth_source_attribution, authentication telemetry (from ATH-005)
  tools user_auth_history
  new events 12 retrieved; shown: 644fcfd5011068a13cc3, 7794c2b19501be2cb80b, 70070eda726d0ffa9b62, 3de8d5b15fb19024a732, 4e51bb11a05d061eaa79, a55b4f1c91b1348a0f1c, +6 more
- attack
  why only eligible specialist; case has ATT&CK mappings and domain evidence has been gathered
  tools lookup_technique, lookup_technique, lookup_technique, lookup_technique
- evidence_verifier
  why validate typed observations against cited telemetry
stopped: no specialist has further useful work on the available evidence
↓
Verdict: Malicious

Reasoning Summary

No model-written reasoning: this run used no model. Its reasoning is the specialist trace in the investigation tree and the findings below.

Executive Summary

This report covers CASE-001, correlating 2 detection finding(s) across 2 host(s) (WS-3250, WS-7003) and 1 account(s) (acct-8592) between 08:00:00 and 08:06:00 UTC on 2026-08-01. The evidence is consistent with activity spanning 4 MITRE ATT&CK tactic(s): Execution -> Persistence -> Credential Access -> Lateral Movement. Each mapping is an interpretation of observed behaviour against a public taxonomy, not a determination that an intrusion occurred. 28 statement(s) below are directly established by telemetry, 10 are evidence-supported inferences, and 0 are explicitly unverified hypotheses requiring analyst confirmation. This report does not authorise or perform any response action. All recommendations below require human review before action is taken.

Attack Timeline

Time	Rule	Severity	User	Host / Movement	ATT&CK	Events
08:00:00	ATH-005	CRITICAL	acct-8592	WS-3250	T1078, T1110.001	`7ae112de50a7ef35212b`, `cbe095d06fbe19e71c8c`, `f2c578af54d2a3cf2d60`, `880b1242f36a26407c74`, `ab491e62927ff53ad2e9`, `ffe190ee68fa49888037`, +7 more
08:06:00	ATH-007	HIGH	acct-8592	WS-3250	T1021.002, T1569.002	`8e3b9127b110d0908581`

Findings

Confirmed (FACT) (28)

Confirmed: Authentication event 1f776b2d12b6e1b38138 records outcome failure.
Evidence: 1f776b2d12b6e1b38138
Confirmed: Event 21cfbf2f84aba973509b records process identity sysmon:2a0296a72747c0b9019b2d5f243aed94.
Evidence: 21cfbf2f84aba973509b
Confirmed: Authentication event 3de8d5b15fb19024a732 records outcome success.
Evidence: 3de8d5b15fb19024a732
Confirmed: Authentication event 4b7981dfd851184e370d records outcome failure.
Evidence: 4b7981dfd851184e370d
Confirmed: Authentication event 4e51bb11a05d061eaa79 records outcome success.
Evidence: 4e51bb11a05d061eaa79
Confirmed: Authentication event 644fcfd5011068a13cc3 records outcome success.
Evidence: 644fcfd5011068a13cc3
Confirmed: Authentication event 70070eda726d0ffa9b62 records outcome success.
Evidence: 70070eda726d0ffa9b62
Confirmed: Authentication event 7794c2b19501be2cb80b records outcome success.
Evidence: 7794c2b19501be2cb80b
Confirmed: Authentication event 7a605231a8b8245ac918 records outcome success.
Evidence: 7a605231a8b8245ac918
Confirmed: Authentication event 7ae112de50a7ef35212b records outcome failure.
Evidence: 7ae112de50a7ef35212b
Confirmed: Authentication event 7e3cdc7f3dd94475bd36 records outcome success.
Evidence: 7e3cdc7f3dd94475bd36
Confirmed: Authentication event 80fa003ab0d4b9fb50d3 records outcome failure.
Evidence: 80fa003ab0d4b9fb50d3
Confirmed: Authentication event 880b1242f36a26407c74 records outcome failure.
Evidence: 880b1242f36a26407c74
Confirmed: Event 8e3b9127b110d0908581 records process identity sysmon:f7a5977e9afb5cc7e63853a79236e480.
Evidence: 8e3b9127b110d0908581
Confirmed: Authentication event 9ad04b5d0a58bac4bdd3 records outcome success.
Evidence: 9ad04b5d0a58bac4bdd3
Confirmed: Authentication event a33f9b609b50fbceb453 records outcome success.
Evidence: a33f9b609b50fbceb453
Confirmed: Authentication event a55b4f1c91b1348a0f1c records outcome success.
Evidence: a55b4f1c91b1348a0f1c
Confirmed: Authentication event a6ae0903817573695f09 records outcome success.
Evidence: a6ae0903817573695f09
Confirmed: Authentication event a9f7b2ac81c66bda1ed3 records outcome success.
Evidence: a9f7b2ac81c66bda1ed3
Confirmed: Authentication event ab491e62927ff53ad2e9 records outcome failure.
Evidence: ab491e62927ff53ad2e9
Confirmed: Authentication event c239520d9ca451aa0921 records outcome failure.
Evidence: c239520d9ca451aa0921
Confirmed: Authentication event cbe095d06fbe19e71c8c records outcome failure.
Evidence: cbe095d06fbe19e71c8c
Confirmed: Authentication event f07d391db002d3c8dc2c records outcome failure.
Evidence: f07d391db002d3c8dc2c
Confirmed: Authentication event f23f1f0ad8cd6cc0a54a records outcome failure.
Evidence: f23f1f0ad8cd6cc0a54a
Confirmed: Authentication event f2c578af54d2a3cf2d60 records outcome failure.
Evidence: f2c578af54d2a3cf2d60
Confirmed: Authentication event f95a47ccf206aedc0264 records outcome success.
Evidence: f95a47ccf206aedc0264
Confirmed: Authentication event ffe190ee68fa49888037 records outcome failure.
Evidence: ffe190ee68fa49888037
Confirmed: Process event 8e3b9127b110d0908581 identifies the instance in 21cfbf2f84aba973509b as its parent.
Evidence: 21cfbf2f84aba973509b, 8e3b9127b110d0908581

Assessed (INFERENCE) (10)

Assessed: Unverified summary: On WS-3250, cmd.exe (PID 500) was started by services.exe under account acct-8592.
Evidence: 8e3b9127b110d0908581
Assessed: Unverified summary: Execution chain on WS-3250: wininit.exe -> services.exe -> cmd.exe.
Evidence: 8e3b9127b110d0908581, 21cfbf2f84aba973509b
Assessed: Unverified summary: Account 'acct-8592' has 25 authentication events (12 failed, 13 successful) across hosts OFFICE-01, WS-3250.
Evidence: 644fcfd5011068a13cc3, 7ae112de50a7ef35212b, cbe095d06fbe19e71c8c, 7794c2b19501be2cb80b, f2c578af54d2a3cf2d60, 70070eda726d0ffa9b62, +19 more
Assessed: Unverified summary: Account 'acct-8592' authenticated from more than one source host: OFFICE-01, WS-7003.
Evidence: 644fcfd5011068a13cc3, 7ae112de50a7ef35212b, cbe095d06fbe19e71c8c, 7794c2b19501be2cb80b, f2c578af54d2a3cf2d60, 70070eda726d0ffa9b62, +19 more
Assessed: The 12 failed authentications for 'acct-8592' followed by success are consistent with the account's password having been guessed rather than with ordinary user error. (confidence 0.85)
Evidence: 7ae112de50a7ef35212b, cbe095d06fbe19e71c8c, f2c578af54d2a3cf2d60, 880b1242f36a26407c74, ab491e62927ff53ad2e9, ffe190ee68fa49888037, +6 more
Assessed: Behaviour cited by ATH-005 is consistent with T1110.001 Brute Force: Password Guessing (Credential Access). Repeated failed authentications for a single account from a single source are consistent with systematically guessing that account's password. (A spray against many accounts would be T1110.003 and is not what was observed.) (confidence 0.90)
Evidence: 7ae112de50a7ef35212b, cbe095d06fbe19e71c8c, f2c578af54d2a3cf2d60, 880b1242f36a26407c74, ab491e62927ff53ad2e9, ffe190ee68fa49888037, +7 more
Assessed: Behaviour cited by ATH-007 is consistent with T1569.002 System Services: Service Execution (Execution). A command interpreter was started by the Service Control Manager, which is the defining behaviour of executing a payload as a Windows service. (confidence 0.90)
Evidence: 8e3b9127b110d0908581
Assessed: Behaviour cited by ATH-005 is consistent with T1078 Valid Accounts (Persistence). A successful authentication followed the failure burst, which is consistent with the account credential now being under adversary control. (confidence 0.60)
Evidence: 7ae112de50a7ef35212b, cbe095d06fbe19e71c8c, f2c578af54d2a3cf2d60, 880b1242f36a26407c74, ab491e62927ff53ad2e9, ffe190ee68fa49888037, +7 more
Assessed: Behaviour cited by ATH-007 is consistent with T1021.002 Remote Services: SMB/Windows Admin Shares (Lateral Movement). Command output was redirected to an administrative share, indicating the service was driven over an authenticated SMB session from another host. (confidence 0.60)
Evidence: 8e3b9127b110d0908581
Assessed: The case spans 4 ATT&CK tactics (Execution -> Persistence -> Credential Access -> Lateral Movement). Progression across multiple tactics is harder to explain as coincidental than activity confined to one. (confidence 0.80)
Evidence: 1f776b2d12b6e1b38138, 4b7981dfd851184e370d, 7ae112de50a7ef35212b, 80fa003ab0d4b9fb50d3, 880b1242f36a26407c74, 8e3b9127b110d0908581, +8 more

Unconfirmed Hypotheses (0)

None.

Recommended Next Steps

Investigative recommendations for a human analyst. No response action has been taken or is authorised by this report.

Retrieve email gateway or web-proxy logs to establish the initial access vector.
Rationale: No detection in this case targets initial access, so the delivery mechanism (e.g. a phishing attachment) is inferred from process lineage rather than confirmed from delivery telemetry.
Based on: MITRE ATT&CK tactic coverage gap: Initial Access
Independently verify account activity on all hosts in scope (WS-3250, WS-7003) rather than relying solely on the correlated case, in case related activity exists that current detections did not flag.
Rationale: This case spans multiple hosts, which increases the possible blast radius.
Based on: case.is_multi_host
Escalate to a human analyst for validation before any remediation action is taken.
Rationale: This system performs read-only investigation only. It has no capability to disable accounts, isolate hosts, or otherwise remediate, and this report is not authorisation to do so.
Based on: system design constraint

Limitations & Scope

Telemetry underlying this report came from: generated_auth_execution. Field coverage depends entirely on what the originating export or sensor captured; this project's canonical schema does not model every field a real EDR product exposes (e.g. file hashes, signer information, session identifiers), and any of those were dropped during normalization.
ATT&CK mappings are interpretations of observed behaviour against a public taxonomy. They indicate that behaviour is consistent with a technique, not that an adversary performed it.
Grouping confidence describes how strongly correlated findings are linked to each other, not whether an intrusion occurred.
No evidence was found for the following ATT&CK tactics: Initial Access, Discovery, Collection, Exfiltration. Their absence may reflect that the activity did not occur, or that available telemetry cannot observe it.
Typed predicates are checked against recorded telemetry; free-text interpretations are not semantically verified. Missing identity is not a confirmed process link, and recorded event order does not establish causation.
No evidence was found for the following tactics: Collection. Their absence may reflect either that the activity did not occur or that we lack the telemetry to see it.

Investigation Trace

Agents run: endpoint, identity, attack; tool calls made: 8

step 1: endpoint -- deterministic priority order; case evidence rests on process_command_line, process_execution, process_lineage telemetry (from ATH-007)
step 2: identity -- deterministic priority order; case evidence rests on auth_source_attribution, authentication telemetry (from ATH-005)
step 3: attack -- only eligible specialist; case has ATT&CK mappings and domain evidence has been gathered
step 4: stop -- no specialist has further useful work on the available evidence
evidence verification: 28 checked observations; 4 summaries reclassified

Evidence Appendix

All 27 telemetry events underlying this report, chronologically.

Event ID	Time	Device	User	Summary
`644fcfd5011068a13cc3`	08:00:00	OFFICE-01	acct-8592	success logon [Interactive (console)] from 10.10.1.5
`7ae112de50a7ef35212b`	08:00:00	WS-3250	acct-8592	failure logon [Network (SMB / share access)] from 10.10.2.8 reason=bad_password
`21cfbf2f84aba973509b`	08:00:00	WS-3250	acct-8592	wininit.exe -> services.exe \| services.exe
`cbe095d06fbe19e71c8c`	08:00:20	WS-3250	acct-8592	failure logon [Network (SMB / share access)] from 10.10.2.8 reason=bad_password
`7794c2b19501be2cb80b`	08:00:29	OFFICE-01	acct-8592	success logon [Interactive (console)] from 10.10.1.5
`f2c578af54d2a3cf2d60`	08:00:40	WS-3250	acct-8592	failure logon [Network (SMB / share access)] from 10.10.2.8 reason=bad_password
`70070eda726d0ffa9b62`	08:00:58	OFFICE-01	acct-8592	success logon [Interactive (console)] from 10.10.1.5
`880b1242f36a26407c74`	08:01:00	WS-3250	acct-8592	failure logon [Network (SMB / share access)] from 10.10.2.8 reason=bad_password
`ab491e62927ff53ad2e9`	08:01:20	WS-3250	acct-8592	failure logon [Network (SMB / share access)] from 10.10.2.8 reason=bad_password
`3de8d5b15fb19024a732`	08:01:27	OFFICE-01	acct-8592	success logon [Interactive (console)] from 10.10.1.5
`ffe190ee68fa49888037`	08:01:40	WS-3250	acct-8592	failure logon [Network (SMB / share access)] from 10.10.2.8 reason=bad_password
`4e51bb11a05d061eaa79`	08:01:56	OFFICE-01	acct-8592	success logon [Interactive (console)] from 10.10.1.5
`f07d391db002d3c8dc2c`	08:02:00	WS-3250	acct-8592	failure logon [Network (SMB / share access)] from 10.10.2.8 reason=bad_password
`1f776b2d12b6e1b38138`	08:02:20	WS-3250	acct-8592	failure logon [Network (SMB / share access)] from 10.10.2.8 reason=bad_password
`a55b4f1c91b1348a0f1c`	08:02:25	OFFICE-01	acct-8592	success logon [Interactive (console)] from 10.10.1.5
`80fa003ab0d4b9fb50d3`	08:02:40	WS-3250	acct-8592	failure logon [Network (SMB / share access)] from 10.10.2.8 reason=bad_password
`a9f7b2ac81c66bda1ed3`	08:02:54	OFFICE-01	acct-8592	success logon [Interactive (console)] from 10.10.1.5
`4b7981dfd851184e370d`	08:03:00	WS-3250	acct-8592	failure logon [Network (SMB / share access)] from 10.10.2.8 reason=bad_password
`f23f1f0ad8cd6cc0a54a`	08:03:20	WS-3250	acct-8592	failure logon [Network (SMB / share access)] from 10.10.2.8 reason=bad_password
`a33f9b609b50fbceb453`	08:03:23	OFFICE-01	acct-8592	success logon [Interactive (console)] from 10.10.1.5
`c239520d9ca451aa0921`	08:03:40	WS-3250	acct-8592	failure logon [Network (SMB / share access)] from 10.10.2.8 reason=bad_password
`7e3cdc7f3dd94475bd36`	08:03:52	OFFICE-01	acct-8592	success logon [Interactive (console)] from 10.10.1.5
`f95a47ccf206aedc0264`	08:04:21	OFFICE-01	acct-8592	success logon [Interactive (console)] from 10.10.1.5
`7a605231a8b8245ac918`	08:04:50	OFFICE-01	acct-8592	success logon [Interactive (console)] from 10.10.1.5
`a6ae0903817573695f09`	08:05:00	WS-3250	acct-8592	success logon [Network (SMB / share access)] from 10.10.2.8
`9ad04b5d0a58bac4bdd3`	08:05:19	OFFICE-01	acct-8592	success logon [Interactive (console)] from 10.10.1.5
`8e3b9127b110d0908581`	08:06:00	WS-3250	acct-8592	services.exe -> cmd.exe \| cmd.exe /Q /c job.cmd 1> \\127.0.0.1\ADMIN$\job.log 2>&1