15 Signs Your Vendor Has Been Breached | UpGuard

This guidance highlights the risks of third‑party breaches and presents 15 indicators a vendor may be compromised (e.g., prior breaches, lack of security transparency, suspicious charges, phishing requests, password reset notices, login failures, unresponsiveness, defacement, unexpected attachments, unusual calls, downtime/DDoS symptoms, odd login hours, DNS hijacking/redirects, and large data transfers), along with verification steps (e.g., breach history lookups) and response actions to minimize impact—stop data loss, mobilize incident response, remediate vulnerabilities, and detect data leaks—emphasizing ongoing vendor risk management and attack surface monitoring.