Realizing that your credentials have been compromised is not a remote possibility—it’s a plausible scenario in any organization or connected personal environment. From the moment credential exposure is suspected or confirmed, every second counts. A rapid, structured, and technically sound response can be the difference between a contained breach and an attack with devastating consequences.
The first thing to understand is that credential compromise is not resolved by simply changing a password. While that may be the immediate and most obvious step, it is not enough to eliminate unauthorized access if the attacker has used persistence techniques, pivoted to other systems, or created alternative accounts. A full containment, forensic analysis, and remediation protocol must be activated. In environments with an established ISMS, this is executed through an incident management procedure aligned with standards like ISO/IEC 27035 and tied to the risk analysis framework of ISO/IEC 27001.
In a corporate environment, the first step should be to immediately notify the security team or SOC (Security Operations Center), if available. In smaller environments, the responsibility falls directly on the user or system administrator. The compromised account must be disabled immediately, or all active sessions must be forcibly terminated. In systems like Azure AD, this may involve revoking persistent access tokens via Microsoft Graph, while in local Active Directory environments, sessions can be forcefully ended and passwords changed. This action should be accompanied by access log analysis, especially those centralized in a SIEM system, to identify suspicious patterns such as off-hours logins, anomalous geolocations, use of unauthorized protocols, or lateral movements within the network.
Credential changes must be comprehensive. Not only should the primary password be changed, but also every password associated with services that used the same credentials or had synchronized authentication. In federated environments, this is especially critical, as compromising an SSO (Single Sign-On) account can expose dozens of corporate applications and external services. Enabling MFA (multi-factor authentication) should be a mandatory follow-up action, if it wasn’t already in place. If it was, it must be verified that it wasn’t bypassed through MFA Fatigue attacks or token theft.
From a technical standpoint, it’s essential to review the compromised system’s logs to assess the incident’s scope. For Windows systems, event logs and local firewall records should be correlated with server logs. For Linux systems, auditing /var/log/auth.log, /var/log/secure, auditd logs, and shell history files is crucial to detect privilege escalation or lateral movement. If the account had admin privileges or SSH access, lateral intrusion must be assumed and a full network node scan should be carried out using tools such as Wazuh, Velociraptor, or manual scripts to check binary integrity, hashes, and suspicious cron jobs.
From a regulatory perspective, if the compromised credentials provided access to personal data protected under GDPR, it must be evaluated whether a security breach affecting the confidentiality, integrity, or availability of that data has occurred. If so, it may be mandatory to notify the relevant authority (such as the AEPD in Spain) within 72 hours. Additionally, affected users must be informed if their rights and freedoms are at real risk. This legal obligation requires accurate documentation of the incident, the analysis performed, the actions taken, and the preventive measures implemented.
From an offensive security perspective, you must think like an attacker: Where else could this account be used? Is it present in a .git-credentials file from any repository? Was it stored in a config.php or any script containing plaintext credentials? Has it been accidentally published on Pastebin, Gist, or similar platforms? Tools like truffleHog, git-secrets, or gitleaks can help audit these risks.
The incident doesn’t end with containment. A proper lessons-learned review must be conducted to understand what failed in the technical and organizational controls. Was the password weak? Was MFA missing? Was the same key reused across services? Did network segmentation fail? Were the logs disabled or not centralized? This analysis should feed the ISMS continuous improvement cycle or, at the very least, drive specific technical actions to reinforce the security posture: credential rotation, system hardening, targeted training, and compliance audits.
Compromising your credentials is not just a personal failure, it’s a chance to test the maturity of your security system, the agility of your response, and the strength of your controls. What matters is not whether it happens, but how you respond when it does.