Which condition is of greatest concern for an IS auditor when reviewing outsourced IT services?

When reviewing outsourced IT services, the concern regarding core activities being outsourced is of paramount importance. Core activities are fundamental to the organization's operations and strategic objectives; hence, outsourcing them can introduce significant risks. These risks include loss of control over critical processes, potential impacts on service quality, and challenges in ensuring compliance with regulatory requirements.

If these core activities are outsourced, the IS auditor must assess whether adequate controls and oversight mechanisms are in place to manage the risks associated with third-party service providers. This includes ensuring that the outsourced provider has the necessary capabilities, security measures, and stability to effectively handle the organization's core functions.

In contrast, while measurable service level agreements, multiple vendors, and contract renegotiations are all relevant considerations in the context of outsourcing, they do not pose the same level of direct risk to the organization’s fundamental operations as the outsourcing of core activities does.