HackingFinancial ServicesFinanceCustomer Data InvolvedGovernment IDIdentity (basic)HighContained

BMO Bank N.A.

bd_224db60eab9ab0ff · schema v1 · pii pii-v1

Severity

High

Discovered

Aug 9, 2023

Filed

Sep 19, 2023

To disclose

6 weeks

Affected · nationwide

56,87935 in this filing

Confidence

66%

Full breach record for BMO Bank N.A. →4 incidents on file

BMO Bank N.A. reported an external system breach (hacking) occurring on May 27, 2023, discovered on August 9, 2023. The incident affected 56,879 individuals, including 35 Maine residents. Acquired data included names and Social Security Numbers. The bank provided written notification on August 31, 2023, and offered one year of credit and identity monitoring through Kroll.

J jump to incidentP pin to compareR raw source

Maine clockDiscovered Aug 9, 2023 → Filed with AG Sep 19, 202341d ⏱ ME AG >30d6 weeks discovery → filing

⚠ AG web formThe discovery date came from the AG web-form field, which is systematically later than the detection date stated in the letter. Treat the clock as indicative.

Incident timeline

undetected · 74 days

discovery → filing · 6 weeks / 41 days

May 27, 2023

Begins

Aug 9, 2023

Discovered

Sep 19, 2023

Filed

vs. sector median

3 wks faster

Tracked as a single-filing incident — the only disclosure on record for this event so far.Confirmed56,879 affectedView incident

Name: BMO Bank N.A.
norm: bmo bank na

Name: BMO Bank N.A.
norm: bmo bank na
Industry: Financial Servicesllm

Discovered: Aug 9, 2023
Breach occurred: May 27, 2023
Undetected for: 74 daysoccurrence → discovery
Materiality determined: —
Notification sent: Aug 31, 2023
Affected individuals: 56,879state + nationwide
Data types: Government IDIdentity (basic)
Data elements: Social Security number
Attack vector: Unauthorized Access
MITRE ATT&CK: T1190 Exploit Public-Facing Application
Threat actor: External
Regulator citations: Filed data breach notice with Maine Attorney General
Initial access: exploit_public_facing

During the incident: Sent written notification to affected consumers
Offered 1 year of Kroll Identity Monitoring Services
Source: Quoted from the filing itself, not independently verified.

Time to disclose: 6 weeks(41 days from discovery to filing)
Compliance flags: ME AG >30d · 41d
Discovery-date grounding: AG web formThe discovery date came from the AG web-form field, which is systematically later than the detection date stated in the letter. Treat the clock as indicative.
Clock breakdown: Statute Window Elapsed Threshold Status
Maine
Discovered: Aug 9, 2023
→ Filed with AG: Sep 19, 2023
41d 30 days (soft) ME AG >30d

Statute	Window	Elapsed	Threshold	Status
Maine	Discovered: Aug 9, 2023 → Filed with AG: Sep 19, 2023	41d	30 days (soft)	ME AG >30d

Status: No extraction artifact recorded for this disclosure.

Evidence ladder

Leak-site claim

Attacker assertion only. Establishes: claim date, group, alleged victim.

Press / market report

Unlocks: incident narrative, operational impact. Still no compliance clock.

State AG / regulator filingThis record

Unlocks: discovery date, data types, affected count, compliance clock.

SEC 8-K / victim statement

Unlocks: materiality, stated response, full audit trail. Ceiling removed.

Source URL: https://www.maine.gov/agviewer/content/ag/985235c7-cb95-4be2-8792-a1252b4f8318/0a95077b-b6ea-4da1-8dd3-5ea2713108c1.shtml
DisclosureLens links to the originating regulator URL — full filing bodies are not redistributed from public surfaces (§4.5).
Filed at: Sep 19, 2023
Raw hash: 48c4cdc9aff22636b281733ec6c05f2b62a91cb74d3b9e8c0caa07a211b4a14d

Reporting entityBMO Bank N.A.

Victim entityBMO Bank N.A.

Incidentdiscovered Aug 9, 2023

Stated responseSent written notification to affected consumers

ComplianceME AG >30d

Extraction provenanceno artifact recorded

Source provenancewww.maine.gov