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Principles are good, but exceptions are OK

Recently we discussed the security of RiskTree with a client, who ran through the NCSC Cloud Security Principles. Since RiskTree is delivered as software-as-a-service, this made sense. One point that arose was the lack of Multi-Factor Authentication (MFA) in use: CSP Principle 10 states that 2FA is ‘considered good practice’, using either a hardware or software token or out-of-band challenge.

We subsequently implemented MFA, using the Time-based One-time Password Algorithm. This allows users to enter a code (either manually, or by scanning a QR code) into an app on their mobile ‘phone, such as Google Authenticator, Microsoft Authenticator, or LastPass Authenticator. We haven’t mandated its use, preferring to let our users decide whether they need it. We’re allowing our users to make the decision about their data; because it isn’t ours to make. To help inform their decision, we used RiskTree to analyse the risks of client data being stolen from RiskTree and put the information onto the site as a demo ( Consequently, some users have enabled it, and some haven’t.

The key question though, and the reason for this blog post, is “what are we actually protecting?”. RiskTree stores no risk data from any of our clients – all the data are handled locally in the browser. For the risk calculations, just a node reference and the six assessment values are transferred to the servers for processing into the risk assessment, and creation of the data charts and visualizations, making the most of the power of cloud processing for the intensive number-crunching part of the work. The only data that we hold about our users is their name, e-mail address, and organization, and we don’t show the latter two, even if a user is logged in. There is no ability for the user to change any of these, so the risk of data tampering has been removed. The only thing that can be achieved by stealing credentials is that the attacker can use RiskTree without paying.

This leads us to conclude that for RiskTree, MFA is overkill. We’ve designed our SaaS to avoid holding any data – to an extent it’s almost like a lambda, in that a user throws some data at it and it returns some results. Whilst the principle of applying MFA to SaaS is sound, it isn’t important if there isn’t anything to protect. Having security principles is a great idea but following them slavishly isn’t. When performing a risk assessment, always keep the context in mind, and be prepared to have exceptions.