mastec.com

Disclosed Oct 14, 2026

Records

50,859

Files

Added

Oct 14, 2026

A data breach affecting MasTec, Inc., a large infrastructure construction company. The archive contains highly sensitive employee and benefits enrollment data including full names, Social Security Numbers (SSNs), dates of birth, home addresses, phone numbers, email addresses, gender, ethnicity codes, health insurance plan details, and dependent information. The data appears to be sourced from health benefits enrollment records. It was cleaned and published on BreachForums by the threat actor Nam3L3ss.

Data found in this dataset

EmailFirst nameLast nameMiddle namePhoneAddressAddress line 2CityStateZIPCountryDOBGenderSuffix

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Source files

Expand any file to inspect its column headers and the field each maps to.

mastec.com_BF/0000.Breached_Info.txt

0 rows

No column mapping was recorded for this file.

mastec.com_BF/EMAILS.csv

13,083 rows

File structure

Notes: Pre-LLM auto-detection: free-form text with visible emails / phones

mastec.com_BF/SSN.txt

0 rows

File structure

Format: CSV·Delimiter: Comma·Has header: no·Quote: "

Notes: File contains only a single column of numeric identifiers with no header; no PII fields present.

mastec.com_BF/mastec15610-SSN.csv

0 rows

File structure

Format: CSV·Delimiter: Comma·Has header: no·Quote: "

Notes: File contains only numeric IDs with no headers, delimiters, or structured columns; appears to be a list of internal identifiers or reference numbers rather than PII records.

mastec.com_BF/mastec15610.csv

27 columns22,066 rows

File structure

Format: CSV·Delimiter: Comma·Has header: yes·Quote: "

Source column	Mapped field	Confidence
10	ssn	high
11	lastName	high
12	firstName	high
13	middleName	high
14	suffix	medium
15	gender	high
16	dob	high
30	address1	high
31	address2	high
33	city	high
34	state	high
35	zip	high
36	country	high
45	phone	high
49	email	high
50	lastName	medium
51	firstName	medium
52	middleName	medium
53	suffix	medium
54	address1	medium
55	address2	medium
57	city	medium
58	state	medium
59	zip	medium
60	country	medium
61	skip	medium
63	skip	medium

Notes: Employee benefits enrollment data from MasTec; 90 columns total, 27 with PII including member and emergency contact details.

mastec.com_BF/mastec15610_EMAILS.csv

11,572 rows

File structure

Notes: Pre-LLM auto-detection: free-form text with visible emails / phones

mastec.com_BF/mastec76628-SSN.csv

0 rows

File structure

Notes: File contains only numeric identifiers with no headers or delimiters; not structured tabular PII data.

mastec.com_BF/mastec76628.csv

29 columns2,624 rows

File structure

Format: CSV·Delimiter: Comma·Has header: yes·Quote: "

Source column	Mapped field	Confidence
10	ssn	high
11	lastName	high
12	firstName	high
13	middleName	high
14	suffix	high
15	gender	high
16	dob	high
30	address1	high
31	address2	high
32	address2	high
33	city	high
34	state	high
35	zip	high
36	country	high
45	phone	high
49	email	high
50	lastName	high
51	firstName	high
52	middleName	high
53	suffix	high
54	address1	high
55	address2	high
56	address2	high
57	city	high
58	state	high
59	zip	high
60	country	high
61	skip	high
63	skip	high

Notes: MasTec health benefits enrollment data; 90 columns total, 29 with PII including member and contact details.

mastec.com_BF/mastec76628_EMAILS.csv

1,514 rows

File structure

Notes: Pre-LLM auto-detection: free-form text with visible emails / phones