Secure authentication

What the control asks

Secure authentication technologies and procedures are to be put in place, driven by the information access restrictions and the access control policy. Purpose: authenticate users and other entities securely whenever they are given access to systems, applications and services. Guidance: choose an authentication technique suited to proving the claimed identity of users, software, messages and other entities, with strength matched to the classification of what is being accessed. When identity must be proven strongly, rely on something other than a password, for example certificates, smart cards, hardware tokens or biometric traits. Access to critical systems should use multi-factor authentication combining something known, held and inherent, which can be extended with rule-based step-up when access comes from an unusual location, device or time. Compromised biometric data should be invalidated, and because biometrics can fail in some conditions (moisture, ageing) at least one alternative technique should be available. Log-on should be designed to minimize unauthorized access by: not revealing sensitive system or application details until log-on succeeds; showing a notice that only authorized users may access the system; giving no help during log-on that could aid an intruder, such as saying which part of the input was wrong; validating the log-on only once all input is complete; resisting brute force through CAPTCHA, forced reset after a set number of failures or lockout; logging failed and successful attempts; raising a security event and alerting the user and administrators when a possible attack on log-on controls is seen; showing or sending separately, after success, when the last successful log-on happened and any failed tries since then; hiding passwords as typed, unless this must be relaxed for accessibility or to avoid repeated lockouts; never sending passwords in clear text across networks; ending sessions after a period of inactivity, especially in public or external locations and on endpoints; and limiting connection times for high-risk applications. Other information: ISO/IEC 29115 covers entity authentication assurance.

Purpose in the standard’s terms, in our words: Ensures users and entities are securely authenticated when granted access to systems, applications and services.

Attribute values in one line: Preventive; Confidentiality, Integrity, Availability; Protect; Identity and access management; Protection.

The five attribute values

These are the published values for this control, from ISO/IEC 27002:2022 clause 4.2 and Annex A Table A.1. Where your own value differs, record the difference and the reason in the same row rather than replacing the published value.

Evidence an auditor asks for

The attribute is a claim about how the control behaves. The evidence is what proves it operates. Keep both, and keep them together.

• An authentication standard linking required authentication strength to information classification and system criticality
• MFA configuration and coverage reports for critical systems, remote access and privileged access, including conditional or risk-based rules
• Log-on configuration showing warning banners, generic error messages, lockout or throttling after failed attempts and masked password entry
• Authentication logs recording successful and failed attempts, with alerting on suspected brute force
• Session timeout and connection time limit settings for high-risk applications and locations
• Evidence that passwords are not transmitted in clear text, for example TLS enforcement on log-on endpoints

Where audits commonly find gaps

• MFA is enabled for some critical systems but legacy protocols allow bypass
• Error messages reveal whether the username or the password was wrong
• No lockout or rate limiting exists on internet-facing log-on pages
• Biometric authentication has no fallback method

What ISO/IEC 27028 changes for this control

It carries a single control type, preventive, which sets what the evidence has to prove. It contributes no detect function, so a control set built from this row alone would not show detection. Its earlier numbering (09.4.2) is kept in the register so an older audit file can still be traced.

The guidance expands how the five values are used; it does not change the control or add a requirement. A register that carries the values and the evidence can answer the attribute question for this control without a new document. A register that does not can add the columns at the next SoA version, with an owner and a review date.

Controls that share its values

• 8.2 Privileged access rights
• 8.3 Information access restriction
• 8.4 Access to source code

Read the five attributes All 93 controls