Single sign-on (SSO) is a method of authentication that allows users to access multiple applications with a single set of login credentials. These credentials are entered into a “centralized” login server (“identity provider” or “IDP”). Applications (“service providers” or “SP”) then refer to the IDP to obtain authentication and/or authorization tokens on behalf of the user. When we talk about SSO using a single set of credentials this federated model is what we are referring to, not using the same credentials everywhere1 or using a pass through authentication like LDAP where the applications have the opportunity to see your credentials on the way through to the authentication server2. The common protocols used in SSO are SAML and to a lesser (but increasing) degree OIDC. The “social sign in with…” options often make sense for consumer applications (with careful consideration of which social provider to choose… Apple, Google and Microsoft are more safe/stable choices than Twitter or Facebook), however Passkeys (a cryptographic, passwordless, proof of identity) is far more portable and future proof than any social sign in options.
The SSO tax refers to the additional cost that organizations may incur when implementing SSO. The primary driver of this cost (and what many people take as the definition of SSO tax) is that many SaaS providers lock SSO behind higher cost tiers - making it more expensive and difficult for organizations to take advantage of this feature. This is a regressive tax - it most often impacts smaller to medium sized businesses - those that would have no need for the higher cost tiers besides the SSO functionality. The SSO Wall of Shame has a list of examples - ranging from a 15% increase to a mind boggling 6300%! When SSO was a new requirement from enterprises to SaaS providers, some uptick might have been reasonable (but not 6300%) to cover some development costs and increases in support calls. However, SSO has been a requirement from large enterprises for many years now and it’s time for the costs to flip. A SaaS provider utilizing SSO reduces its overall cyber risk. It won’t directly be vulnerable to credential stuffing attacks3, won’t have credentials to lose and won’t need to invest in a custom MFA solution. Conversely, creating financial incentives for customers to use SSO with their applications can shift the burden of defending against credential stuffing, risk management and MFA enforcement back on their customers.
In that world, the main cost associated with SSO becomes the need for additional infrastructure and resources. Organizations may need to purchase and maintain servers and other hardware to support the SSO system, which can add to the overall cost of the system. Additionally, SSO systems may require additional software and licensing fees, which can also add to the cost. These costs can be reduced by utilizing a commercial, hosted SSO provider. Even the lowest business tier Microsoft365 or Google Workspace accounts provide very capable SAML identity providers. For more specialized SSO solutions, Okta is a very popular option. Another example is Duo Security, who provide an SSO identity provider to make it easier to integrate their MFA solution.
Another cost associated with SSO is the need for specialized personnel to manage and maintain the system. Organizations may need to hire additional staff or contract with third-party vendors to manage and maintain the SSO system, which can add to the overall cost of the system.
Despite the SSO tax, many organizations choose to implement SSO systems because of the benefits they provide. SSO systems can help to improve security by reducing the number of login credentials that users need to remember and manage. Having a centralized identity provider is a solid foundation to build a Zero Trust environment from - one place to enforce multi factor (or move to a passwordless solution) as well as an opportunity to perform granular authorization of both users and devices. Additionally, SSO systems can help to improve productivity by allowing users to access multiple applications with a single set of login credentials.
In conclusion, the SSO tax refers to the additional cost that organizations may incur when implementing SSO systems. While the SSO tax can be significant, many organizations choose to implement SSO systems due to the benefits they provide such as improved security and productivity. Procella strongly believes in SSO as a fundamental part of an organizations security posture, but those organizations should be aware of the costs involved before starting on an SSO project, and push their SaaS providers to include standards based single sign-on at base level tiers. Procella calls for all SaaS providers to ditch their component of the SSO tax and lead from the front in freely supporting and encouraging enterprise SSO and consumer passwordless authentication methods.
Also a bad idea. It makes your staff more susceptible to phishing attacks and gives applications private data that they don’t need! ↩︎
Taking credentials from another breach and programmatically trying to use those credentials against your application ↩︎
affiliate link - but you get 25% off first year for business accounts. ↩︎