--- title: CAD & BIM Security Tips to Withstand Ransomware Attacks description: Discover essential CAD and BIM security tips to protect your architecture firm from ransomware attacks with The Millennium Group Computing. image: https://www.tmgcinc.com/hubfs/BIM%20Security.webp --- [Skip to the main content.](https://www.tmgcinc.com/blog/bim-security-withstand-ransomware-attack#main-content) [![TMGC\_Logo\_Main\_V1](https://www.tmgcinc.com/hs-fs/hubfs/Logos/TMGC_Logo_Main_V1.webp?width=130&height=112&name=TMGC_Logo_Main_V1.webp "TMGC_Logo_Main_V1")](https://www.tmgcinc.com/) [![TMGC\_Logo\_Main\_V1](https://www.tmgcinc.com/hs-fs/hubfs/Logos/TMGC_Logo_Main_V1.webp?width=150&height=129&name=TMGC_Logo_Main_V1.webp "TMGC_Logo_Main_V1")](https://www.tmgcinc.com/) - [Fractional IT Services](https://www.tmgcinc.com/fractional-it-services) - What We Do - [Complete IT Management](https://www.tmgcinc.com/fractional-it-services) - [Cybersecurity](https://www.tmgcinc.com/managed-cybersecurity-services) - [Service Desk](https://www.tmgcinc.com/it-help-desk-services) - [Data Protection & Recovery](https://www.tmgcinc.com/data-backup-recovery) - [Cloud & Hosting](https://www.tmgcinc.com/managed-cloud-hosting-services) - [Compliance Management](https://www.tmgcinc.com/it-compliance-services) - [IT Infrastructure](https://www.tmgcinc.com/it-infrastructure-management) - [Licensing & Software Management](https://www.tmgcinc.com/it-licensing-management) - [Device Management](https://www.tmgcinc.com/it-device-management) - Industries - [Manufacturing](https://www.tmgcinc.com/managed-it-services-manufacturing) - [AEC](https://www.tmgcinc.com/architecture-engineering-construction-it-services) - [Financial Services](https://www.tmgcinc.com/it-support-financial-services) - [Medical](https://www.tmgcinc.com/managed-it-services-medical-practices) - [Defense Contractors](https://www.tmgcinc.com/it-support-defense-contractors) - [Private Equity](https://www.tmgcinc.com/it-services-private-equity) - Resources - [About Us](https://www.tmgcinc.com/about) - [Blog](https://www.tmgcinc.com/blog) - [Case Studies](https://www.tmgcinc.com/case-studies) - [Guide to CMMC Compliance](https://www.tmgcinc.com/cmmc-compliance-everything-defense-contractors-need-to-know-in-2026) - [Guide to Workplace AI Security](https://www.tmgcinc.com/workplace-ai-security-guide) - [AI Readiness Quiz](https://www.tmgcinc.com/ai-security-readiness-quiz-tmgc) [GET STARTED](https://www.tmgcinc.com/contact) Toggle Menu Toggle Menu [GET STARTED](https://www.tmgcinc.com/contact) - [Fractional IT Services](https://www.tmgcinc.com/fractional-it-services) - What We Do - [Complete IT Management](https://www.tmgcinc.com/fractional-it-services) - [Cybersecurity](https://www.tmgcinc.com/managed-cybersecurity-services) - [Service Desk](https://www.tmgcinc.com/it-help-desk-services) - [Data Protection & Recovery](https://www.tmgcinc.com/data-backup-recovery) - [Cloud & Hosting](https://www.tmgcinc.com/managed-cloud-hosting-services) - [Compliance Management](https://www.tmgcinc.com/it-compliance-services) - [IT Infrastructure](https://www.tmgcinc.com/it-infrastructure-management) - [Licensing & Software Management](https://www.tmgcinc.com/it-licensing-management) - [Device Management](https://www.tmgcinc.com/it-device-management) - Industries - [Manufacturing](https://www.tmgcinc.com/managed-it-services-manufacturing) - [AEC](https://www.tmgcinc.com/architecture-engineering-construction-it-services) - [Financial Services](https://www.tmgcinc.com/it-support-financial-services) - [Medical](https://www.tmgcinc.com/managed-it-services-medical-practices) - [Defense Contractors](https://www.tmgcinc.com/it-support-defense-contractors) - [Private Equity](https://www.tmgcinc.com/it-services-private-equity) - Resources - [About Us](https://www.tmgcinc.com/about) - [Blog](https://www.tmgcinc.com/blog) - [Case Studies](https://www.tmgcinc.com/case-studies) - [Guide to CMMC Compliance](https://www.tmgcinc.com/cmmc-compliance-everything-defense-contractors-need-to-know-in-2026) - [Guide to Workplace AI Security](https://www.tmgcinc.com/workplace-ai-security-guide) - [AI Readiness Quiz](https://www.tmgcinc.com/ai-security-readiness-quiz-tmgc) [Linkedin](https://www.linkedin.com/company/the-millennium-group-computing/) 6 min read # CAD & BIM Security Tips to Withstand Ransomware Attacks [Tony DiDonato](https://www.tmgcinc.com/blog/author/tony-didonato) : October 2, 2026 [architecture](https://www.tmgcinc.com/blog/tag/architecture) ![CAD & BIM Security Tips to Withstand Ransomware Attacks](https://www.tmgcinc.com/hubfs/BIM%20Security.webp) BIM security is how an [architecture firm](https://www.tmgcinc.com/architecture-engineering-construction-it-services) protects its models, the files linked to them, and the version history behind them from being stolen or locked up. Most firms I talk to assume their backups have this covered, but I've been doing this since before Y2K (I know, you’d never guess). That’s long enough to tell you that for a lot of firms, that assumption won't survive a ransomware attack. A Revit project is never a single file. It's a central model, a local copy on every designer's machine, and a web of linked consultant models, CAD backgrounds, and families. Ransomware hits all of it at once, and getting a project back to where your team left off is a much bigger job than restoring a folder of spreadsheets. We already covered why [architecture firms have become a bigger ransomware target](https://www.tmgcinc.com/blog/why-architecture-firms-are-becoming-a-bigger-ransomware-target). This post picks up where that one left off: what happens to your files once an attack lands, and what it takes to get them back.   ## **Key Takeaways** - A Revit project is a network of linked files, so restoring one model rarely brings a project back to working order - Cloud sync tools like OneDrive can copy encrypted files over your good ones, and the built-in restore window only reaches back 30 days - Attackers tried to compromise backups in 94% of ransomware attacks and succeeded 57% of the time - When backups were compromised, median recovery costs jumped from $375,000 to $3 million (!!!) - BIM security comes down to backups kept off your network, tested restores, and tight access to project folders   ## **Table of Contents** 1. What Is BIM Security? 2. What Does Ransomware Do to a Revit Project? 3. Why Cloud Sync Won't Save You by Default 4. Why Do Attackers Go After Your Backups First? 5. How Long Does It Take to Get BIM Files Back? 6. Building BIM Security That Holds Up   ## **What Is BIM Security?** BIM security is the set of controls that keeps building information models, the files they depend on, and their version history safe from theft and ransomware. It covers where models are stored, who can open them, how they're shared with consultants, and how quickly they can be restored. There's an international standard for this, [ISO 19650-5](https://www.iso.org/standard/74206.html), which lays out a security-minded approach to managing BIM information. You'll mostly see it on large public and infrastructure projects. For a 20 or 40-person firm, the practical version is simpler: ***know where your models live, control who can touch them, and make sure you can bring them back.*** The theft side matters too. Unreleased designs and bid numbers carry value on their own, and attackers know it. In Coalition's claims data, [70% of ransomware claims involved stolen data on top of encryption](https://www.coalitioninc.com/announcements/2026-cyber-claims-report), and those claims cost twice as much. We covered that double extortion angle in our [ransomware post](https://www.tmgcinc.com/blog/why-architecture-firms-are-becoming-a-bigger-ransomware-target), so now let’s talk about recovery.   ## **What Does Ransomware Do to a Revit Project?** Ransomware encrypts the central model, every local copy it can reach, and the linked files the model depends on. Even if you restore the central file, broken links to consultant models, CAD backgrounds, and shared families can leave the project unusable until each piece is recovered to the same point in time. Here's how that plays out in a typical shared project: 1. The central model sits on your file server. 2. Each designer works in a local copy on their own machine and syncs changes back to central throughout the day. 3. Revit keeps its own backup folder for the central model, and it sits right next to the central file on that same server. 4. When ransomware reaches the server, it encrypts the central model and Revit's backup folder together, since they live in the same place. 5. Any designer machine that gets hit loses its local copy too, along with whatever work hadn't been synced back yet. Then there are the links. Your model probably references a structural model from one consultant, an MEP model from another, a survey or site plan in DWG, and a library of families your team has built up over years. If your backup restores the architectural model from Tuesday and the structural link from two weeks ago, you've brought back files that don't agree with each other. Someone then spends days reconciling them before the project can move forward.   ## **Why Cloud Sync Won't Save You by Default** A lot of firms moved project files into OneDrive, SharePoint, or another sync tool over the last few years, and many assume that means ransomware can't touch them. Sync tools do exactly what they're designed to do, which is copy changes everywhere as fast as possible. When a laptop gets encrypted, the encrypted versions sync up to the cloud and back down to every other machine connected to that folder. Microsoft does give you ways to recover. OneDrive's Files Restore can roll a library back [within the last 30 days](https://learn.microsoft.com/en-us/compliance/assurance/assurance-shared-ransomware-protection), and version history keeps older copies of each file. But Microsoft's own guidance describes this as a shared responsibility, and it recommends customers look at a separate backup on top of what's built in. If nobody notices the damage for five weeks, or the attacker deletes versions from inside the account, the built-in tools won't reach far enough. Autodesk Docs and Autodesk Construction Cloud work the same way. You can [view and restore earlier versions of a cloud model](https://help.autodesk.com/view/RVT/2022/ENU/?guid=GUID-A5D26FC2-A8DE-4D94-ACD1-5A0BD66DC869), which helps with a single bad sync. Restoring an entire project version by version is slow, and an attacker logged in with your project admin's credentials has the same power to delete as your project admin. That's why [credential theft](https://www.tmgcinc.com/blog/guide-business-credential-theft) belongs in any BIM security conversation. Here's how each place your BIM files live holds up:   | **Where Your Files Live** | **What Ransomware Can Do** | **What Brings Them Back** | | --- | --- | --- | | Office file server (central models) | Encrypts the central model and Revit's backup folder beside it | An offline or immutable backup from a known clean point | | Designer workstations (local copies) | Encrypts local copies and wipes out work not yet synced to central | Rebuild the machine and create a new local from the restored central | | OneDrive or SharePoint synced folders | Syncs encrypted versions to the cloud and every connected machine | Files Restore within 30 days, or a separate Microsoft 365 backup | | Autodesk Docs or ACC | A stolen admin login can delete or overwrite versions | Version history, plus a separate backup of project data | | Backup appliance on the same network | Gets targeted and wiped out first | Nothing, which is why it can't be your only copy |   ## **Why Do Attackers Go After Your Backups First?** Attackers go after backups because a firm that can restore on its own has no reason to pay. [Sophos found](https://www.sophos.com/en-us/blog/the-impact-of-compromised-backups-on-ransomware-outcomes) attackers tried to compromise backups in 94% of ransomware attacks and succeeded 57% of the time, and firms that lost their backups were far more likely to pay. What happens next is hard to ignore.   > When backups were compromised, the median ransom demand doubled, from $1 million to $2.3 million. The share of victims who paid nearly doubled, from 36% to 67%. Median recovery costs jumped from $375,000 to $3 million, roughly eight times higher.   [Architecture firms](https://www.tmgcinc.com/blog/it-support-for-architects) are especially exposed here because of file size. Pushing hundreds of gigabytes of BIM data offsite every night is slow, so plenty of firms settle for a backup appliance sitting on the same network as the file server. That's convenient on a normal Tuesday. During an attack, it's the first thing the attacker finds.   ## **How Long Does It Take to Get BIM Files Back?** Recovery time depends on how much data you have, where your clean copy lives, and whether you've ever practiced the restore. Firms with offline, tested backups sized for BIM can have active projects running again in days. Firms relying on a single on-network backup can be looking at weeks, or files that never come back. In our [ransomware post](https://www.tmgcinc.com/blog/why-architecture-firms-are-becoming-a-bigger-ransomware-target), we noted that average recovery runs about 24 days, while most design firms can only go about five days without their project files. The order you restore in decides how much of that gap you feel: 1. **Projects with the nearest deadlines first:** Permit submittals and client deliverables come before anything in the archive. 2. **Linked files to the same point in time:** Consultant models, DWG backgrounds, and families need to match the restored central model. 3. **Verify before anyone gets back to work:** Open each model, check that links resolve, and confirm the files are clean. Microsoft's guidance is to clean every device before restoring, or the files can get encrypted again. We've seen how much the setup matters with [Naos](https://www.tmgcinc.com/case-studies), an architecture firm we've supported for years. When Naos moved to hybrid and remote work, we set things up so their team works on firm-managed computers that connect into servers we host in our data center, instead of syncing copies of project files to home laptops. That gives ransomware far fewer copies to reach and gives us one controlled place to restore from.   ## **Building BIM Security That Holds Up** None of this requires an enterprise budget, but it does deserve some dedicated time to setup properly. - **Backups sized for BIM and kept off your network:** Use offline or immutable copies that an attacker can't reach from a compromised server. Our [data backup and recovery](https://www.tmgcinc.com/data-backup-recovery) service runs out of a private data center for this reason. - **Test a full project restore every quarter:** Restore the whole project, links included, and time how long it takes. - **Tight access to project folders:** Give people access to the projects they're working on, and keep admin accounts separate from everyday accounts. - **Phishing-resistant logins for anyone with admin rights:** That covers your file server, your Microsoft 365 tenant, and your ACC hub. [Passkeys](https://www.tmgcinc.com/blog/passkeys-vs-passwords-the-difference-in-stopping-credential-theft) are the strongest option. - **Clean up consultant access when projects close:** The same roll-off habits we recommend for [Autodesk license management](https://www.tmgcinc.com/blog/autodesk-license-management-the-it-cost-most-architecture-firms-miss) apply to folder access and shared links. - **A written recovery order:** Decide now which projects come back first, so nobody's making that call at 2am during an attack. This is part of what [real IT support for architects](https://www.tmgcinc.com/blog/it-support-for-architects) should already include, and it's how we build every [architecture firm's IT](https://www.tmgcinc.com/architecture-engineering-construction-it-services) under one flat monthly rate. 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