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Table of Contents
- What Is Access Management?
- What Is Access Control?
- What Is Passwordless Authentication?
- What Is CIAM (Customer Identity and Access Management)?
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Authentication and Authorization Explained
- Authentication and Authorization Explained
- Differentiating Authentication from Authorization
- Authorization Models: RBAC, ABAC, and Policy Enforcement
- Lateral Movement and Attacker Workflow
- Cloud Security Implications for Authorization
- Zero Trust Alignment with Access Control
- Authentication and Authorization FAQs
- What is BeyondCorp?
- What is the Evolution of Multifactor Authentication
- What Is the Principle of Least Privilege?
- What Is Cloud Infrastructure Entitlement Management (CIEM)?
- What is Multifactor Authentication (MFA) Implementation?
- What Is Identity and Access Management (IAM)?
What Is Single Sign-On (SSO)?
3 min. read
Table of Contents
Single sign-on (SSO) is an authentication method that allows users to access multiple applications and services with a single login. In practice, SSO centralizes authentication through an identity provider (IdP), so users sign in once and gain access to approved apps without re-authenticating each time. SSO is often paired with multifactor authentication (MFA) to strengthen access security and reduce password reset chaos.
Key Points
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One login, many apps: Users authenticate once via an IdP, then access approved applications without repeated sign-ins. -
Less password sprawl: Fewer passwords mean fewer resets, fewer sticky-note “security strategies,” and fewer weak/reused credentials. -
Better security when combined with MFA: SSO reduces password exposure, while MFA reduces account takeover risk if credentials are stolen. -
Centralized control and visibility: Access policy, provisioning signals, and audit trails are easier to manage when authentication is unified. -
Bigger blast radius if misconfigured: If an SSO account is compromised and controls are weak, attackers can quickly gain broad access.
Why Single Sign-On Matters
Modern employees use a variety of tools, including legacy enterprise applications, cloud services, SaaS platforms, and mobile apps. Since each application requires a unique login, comprehensive identity security is crucial, as organizations face threats from three directions:
User experience problems
Users end up managing too many passwords, which leads to predictable shortcuts and easy wins for attackers.
- Credential stuffing thrives on password reuse (Credential stuffing)
- Brute force targets weak passwords (Brute force)
- Phishing tricks users into handing over credentials (Phishing)
- Credential-based attacks turn one stolen login into a foothold (Credential-based attack)
IT and security operations problems
When identity is siloed across apps, onboarding and access changes are manual, slow, and error-prone. That’s how you get:
- inconsistent access policies
- too many help-desk tickets
- messy offboarding
- privilege creep (access that lingers after role changes)
For the broader control layer, see access management and access control (Access management, Access control).
How Single Sign-On Works
SSO typically involves three building blocks:
- Identity provider (IdP): Verifies the user and issues a trusted authentication token. (See IdP overview in What is IAM?)
- Service provider (SP): The application the user is trying to access.
- Federation protocol: The "language" the IdP and apps use to trust each other.
Common SSO protocols include:
- SAML: commonly used for enterprise SSO (example reference on SAML enabling SSO in Palo Alto Networks content: Code security overview referencing SAML and SSO)
- OAuth 2.0 and OpenID Connect (OIDC): common for modern web and cloud authentication flows (OIDC overview in Palo Alto Networks content: OpenID Connect section)
A typical flow looks like this:
- A user tries to access an app.
- The app redirects the user to the IdP.
- The IdP authenticates the user (often with MFA).
- The IdP issues a signed assertion/token to the app.
- The app grants access based on the token and policy.
SSO Features and Functions
Modern SSO solutions simplify access by centralizing authentication and integrating with common enterprise directories and credential stores.
- Directory integrations: Active Directory, LDAP, and cloud directories to maintain consistent identities across apps.
- Federated identity: Standards-based trust between organizations and apps using SAML, OAuth, and OIDC.
- Self-service capabilities: Portals for password resets, access requests, and basic account management to reduce help-desk load.
- Policy-based access control: Centralized rules for who can access what, from where, and under which conditions.
Business Benefits of Single Sign-On
- Superior user experience: Users get fast, consistent access to apps with fewer login prompts and fewer password resets.
- Simplified IT operations: Centralized authentication reduces manual provisioning work and lowers support overhead.
- Increased productivity and collaboration: Easier access to tools improves day-to-day workflows and simplifies partner access when federation is used.
- Risk reduction: Less password sprawl and fewer identity silos reduce the number of common paths to account takeover.
Security Cautions and Best Practices
SSO amplifies whatever controls you put behind it. When implemented with strong authentication, granular access controls, and monitoring, it reduces risk and friction. When it’s misconfigured or under-protected, it can turn one compromised login into fast, broad access across your environment.
- Single point of failure risk: If the SSO identity is compromised, attackers can quickly gain access to multiple applications.
- Mitigation with MFA: Use MFA for high-risk access and critical apps (What is MFA?).
- Align with Zero Trust: Treat access as a continuous decision, not a one-time login event (Zero Trust architecture).
- Reduce privilege creep: Ensure access changes and offboarding are enforced and audited through IAM governance practices (What is IAM?).
- Monitor and respond: Track unusual login patterns, new geographies, suspicious IP ranges, and repeated MFA prompts.
SSO FAQs
SSO reduces login counts by centralizing authentication. MFA adds an extra layer of verification to reduce account takeover risk. They are commonly used together.
Not necessarily. Some SSO deployments still rely on a primary password at the IdP. Many organizations combine SSO with stronger methods (like phishing-resistant MFA or passwordless) to reduce password exposure.
It can be very secure when paired with MFA, strong policy, and monitoring. Without those, SSO can increase the impact of a compromised account.
Most modern SaaS apps support SSO via SAML or OIDC. Many legacy apps can be integrated through connectors or gateways depending on the environment.
