MasTec Discloses Data Breach Affecting Over 25,000 Individuals
MasTec Inc., a Florida-based infrastructure engineering and construction firm, recently reported a data breach impacting 25,220 individuals across the U.S., including 1,160 South Carolina residents and 11 Maine residents. The breach was formally disclosed to state attorneys general on June 5, 2026, with affected consumers notified via written letters beginning May 11, 2026.
The incident came to light in October 2025, when MasTec detected suspicious network activity. A subsequent investigation, conducted with third-party cybersecurity experts, confirmed that an unauthorized party had accessed a limited portion of the company’s systems during August 2025. On October 29, 2025, the CL0P ransomware group claimed responsibility, posting on the Tor network to assert it had exfiltrated sensitive data.
MasTec later engaged a data-review firm to analyze the compromised files, receiving final results in February 2026. While the publicly available notice did not specify exact data categories, affected individuals were informed of the types of personal information exposed in their cases, which may have included names, Social Security numbers, dates of birth, and financial details.
In response, MasTec offered impacted individuals a free membership to Financial Shield, a credit and identity-theft monitoring service. Enrollment required a personalized activation code and adherence to a specified deadline. For additional support, the company established a dedicated response line at 844-953-0840.
Source: https://www.claimdepot.com/data-breach/mastec-2026
MasTec cybersecurity rating report: https://www.rankiteo.com/company/mas-tec
"id": "MAS1780929338",
"linkid": "mas-tec",
"type": "Ransomware",
"date": "8/2025",
"severity": "100",
"impact": "4",
"explanation": "Attack with significant impact with customers data leaks"{'affected_entities': [{'customers_affected': '25220',
'industry': 'Infrastructure Engineering and '
'Construction',
'location': 'Florida, USA',
'name': 'MasTec Inc.',
'type': 'Corporation'}],
'attack_vector': 'Network intrusion',
'customer_advisories': 'Free membership to Financial Shield (credit and '
'identity-theft monitoring service) offered to '
'affected individuals',
'data_breach': {'data_exfiltration': 'Yes',
'number_of_records_exposed': '25220',
'personally_identifiable_information': 'Yes',
'sensitivity_of_data': 'High',
'type_of_data_compromised': ['Names',
'Social Security numbers',
'Dates of birth',
'Financial details']},
'date_detected': '2025-10',
'date_publicly_disclosed': '2026-06-05',
'description': 'MasTec Inc., a Florida-based infrastructure engineering and '
'construction firm, reported a data breach impacting 25,220 '
'individuals across the U.S. The breach was detected in '
'October 2025, with unauthorized access occurring in August '
'2025. The CL0P ransomware group claimed responsibility and '
'exfiltrated sensitive data. Affected individuals were '
'notified via written letters beginning May 11, 2026.',
'impact': {'data_compromised': 'Personal information including names, Social '
'Security numbers, dates of birth, and '
'financial details',
'identity_theft_risk': 'High',
'payment_information_risk': 'High',
'systems_affected': 'Limited portion of company’s systems'},
'investigation_status': 'Completed',
'motivation': 'Data exfiltration',
'ransomware': {'data_exfiltration': 'Yes', 'ransomware_strain': 'CL0P'},
'references': [{'source': 'MasTec Data Breach Notice'}],
'regulatory_compliance': {'regulatory_notifications': 'Disclosed to state '
'attorneys general on '
'June 5, 2026'},
'response': {'communication_strategy': 'Written letters to affected '
'individuals beginning May 11, 2026',
'third_party_assistance': 'Third-party cybersecurity experts and '
'data-review firm'},
'threat_actor': 'CL0P ransomware group',
'title': 'MasTec Data Breach Affecting Over 25,000 Individuals',
'type': 'Data Breach'}