Contractor Downloads, API-Only CASB and Shadow IT
Verdant Consulting has 2,800 employees and 900 contractors. Microsoft 365 and Salesforce are sanctioned and connected to Forcepoint Cloud App Security through API integrations; there is no inline proxy for SaaS traffic. Contractors work from personal laptops and phones and authenticate through Entra ID. Last month a departing contractor downloaded 4,000 client files from a SharePoint site to a personal laptop over three evenings. The CASB flagged it after the fact and legal is still assessing exposure. The partner group now requires that files labelled Confidential cannot be downloaded to unmanaged devices at all, only viewed, with watermarks where possible. Separately, proxy logs ingested for cloud discovery show 320 shadow IT apps; the largest upload volume goes to personal Dropbox accounts used by the M&A team, whose deal documents are under legal hold.
1. Can the API-connected CASB block that download in real time? Design the control that actually meets the partner group's requirement.
Read the worked answer
No. An API connection reads the tenant's data and activity after the fact. It can detect the download, quarantine the file, remove sharing, revoke sessions and alert, but it never sits in the HTTPS session, so it cannot interrupt a download while it happens. Anyone promising real-time blocking from API mode alone has confused visibility with enforcement.
The enforcement point must be in the session or on the device:
- Identity provider conditional access. Require a compliant or managed device for SharePoint and OneDrive, and apply app-enforced restrictions so unmanaged devices get browser-only, view-only access with no download, print or sync. This is the primary control and it covers the contractor scenario.
- Watermarking comes from the same app-enforced restrictions or a sensitivity label with content marking; do not promise dynamic per-user watermarks unless the platform supports it.
- Close the sync-client gap. The OneDrive sync client does not traverse the browser session, so conditional access alone can be bypassed by a managed device that then copies files elsewhere. Endpoint DLP on managed devices covers that path.
- Keep the API CASB for what it is good at: at-rest scanning, oversharing detection, quarantine, anomaly detection such as the three-evening download pattern.
Pilot on a contractor group before enforcing globally, and prepare a helpdesk script for legitimate unmanaged-device requests.
2. The M&A team is uploading deal documents to personal Dropbox. What is your sequence of actions, and why is a company-wide block the wrong first move?
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This is a legal exposure and an insider-risk question before it is a policy question.
First, establish facts. Use cloud discovery and DLP incident search to determine what actually left: file names, hashes, volumes, timing, and which accounts. Preserve that evidence; do not let clean-up destroy the record. Notify legal and the insider-risk process immediately, because the documents are under legal hold and personal cloud copies may now be part of discovery obligations.
Then contain, narrowly. Block uploads to unsanctioned storage for the M&A group specifically, using inline proxy control if available, otherwise endpoint DLP plus browser-level controls for managed devices. Review and revoke OAuth grants to third-party apps, which are a common alternate path.
Then provide the legitimate route. M&A needs external collaboration; if you only block, they will move to personal email or a phone camera. Provision a sanctioned workspace with the required controls and show them how to request external sharing.
Why not company-wide. A blanket block on 320 apps creates a wave of helpdesk tickets, breaks legitimate workflows, and drives the same behaviour to channels you cannot see. Risk-based sequencing - sensitive groups and sensitive destinations first - keeps enforcement credible and gives you time to classify the rest of the shadow IT inventory by app risk score, data volume and OAuth scope rather than by name.
3. What would you put in place to keep this from recurring, and which metrics would you take to the partner group after two quarters?
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Recurrence here is a governance failure as much as a technical one: contractors with personal devices, no session control, and no owner for shadow IT.
Standing controls:
- Conditional access baseline for all external identities, with a documented exception path and a review of guest accounts every quarter.
- A sanctioned-app catalogue with an approval workflow, so the answer to 'I need to share files' is a product, not a prohibition.
- OAuth consent restricted so users cannot grant third-party apps access to mail or files without review.
- Departing-user process that revokes sessions and checks recent large downloads before the last day, not after.
- Sensitivity labelling tied to DLP rules, so enforcement follows the data rather than the app.
Metrics after two quarters:
- Percentage of file-sharing activity in sanctioned apps versus unsanctioned, trending up.
- Unsanctioned upload incidents per 100 users, split by business unit.
- Median time from detection to containment, with the contractor case as the baseline.
- Contractor devices enrolled or using view-only access, as a coverage number.
- Number of shadow IT apps with unknown risk still receiving corporate data.
Report the trend and the residual risk, including the API-only visibility gap on encrypted personal channels. The partner group will judge the programme on whether the next departure is detected in minutes rather than days.