Sharing and collaborating safely

Module 7: Access, suppliers and cloud · Reading time: 10 minutes

Learning objective: After this lesson you can choose the safest way of sharing for any situation: internal sharing with an account, a personal share, or a public link with a password, expiry date and download limit, and you know what you'd better not send by email.
Key terms: share link, public link, expiry date, password on link, download limit, file request, encrypted sending, minimal data

Sharing is the new attachment

In the past, you sent a document as an attachment to an email. These days, you increasingly share a link to a file in your cloud storage instead. That has big advantages: no copies floating around, always the latest version, even large files, and you can revoke access later. An attachment, once sent, can never be taken back.

But a link has its own risk too. A public link works for anyone who has it. If it's forwarded, pasted into a group chat, or ends up in a hacked mailbox, that other person can access it too. A link without a password or expiry date that was created for a job three years ago often still works.

Three ways of sharing

Almost every cloud storage service has three types of sharing. Always choose the most restricted one that works.

Internal sharing is the safest: there's no link that can leak, and if the colleague leaves and their account is disabled (lesson 7.1), access is gone immediately. With a personal share, each recipient gets their own link, so you can see per person who you're sharing with and stop sharing per person.

The settings of a link

If it does have to be a public link, set it up deliberately. Most services have these options:

• Permissions: view only, or also edit. Choose view only by default. That's enough for reading along.
• Password on the link: whoever opens the link first has to enter a password. Send that password via a different channel than the link: the link by email, the password by text message or phone. Whoever only intercepts the email then has nothing yet.
• Expiry date: after that date, the link stops working. That way you don't have to remember to tidy it up.
• Download limit: the link stops working after a certain number of downloads.
• Hide download: the recipient doesn't see a download button. That's not real protection: whatever someone can see, they can also capture, even if it's just a screenshot.
• A label or name for the link, so you know later what it was for.

Also, share the file itself, not the folder around it, unless the other person really should see everything in that folder. A link to the folder "Clients 2026" for a single quote is a classic leak.

A file request

If a client or supplier needs to deliver something to you, use a file request (also known as an upload link or "drop-off only"). The other person can upload files but doesn't see what's already in the folder. Give each client their own folder and their own request, with a password and expiry date. That way client A can never see client B's documents, and you immediately know who sent what.

What shouldn't go by ordinary email

An ordinary email can be compared to a postcard that passes through a few post offices. The connection between mail servers is often encrypted, but after that the email sits readable in the mailboxes of sender and recipient, often for years, and a mistyped address is enough to cause a data breach (lesson 8.2).

So don't send as an ordinary attachment:

• copies of passports or identity documents;
• medical data or health-related data;
• payslips, salary overviews and national identification numbers;
• passwords and recovery codes (those belong in a password manager, possibly via a shared vault, lesson 2.2).

Instead, use a share with a password and expiry date from your own storage, or a service that supports encrypted sending, where only the recipient can open the message. There are various types: encryption built into your email program or email package, a secure messaging service, or a separate service for sending encrypted files.

Minimal data

The best protection against a leak is data you don't share. Ask yourself with every share: does the other person really need this? An accountant needs your invoices, not your entire client database. A landlord wants to know that someone exists, but doesn't always need a copy of their passport. If a copy of an identity document is still needed, you can mask the national identification number and photo and add a watermark stating the purpose and date. Check whether a government agency in your country offers a free app for this (in the Netherlands this is KopieID, from the Dutch government).

Tidying up

Links pile up. Many services show an overview of everything you've shared. Review this once a quarter:

1. Stop all public links without an expiry date that are no longer needed.
2. Check whether external people still have access to folders from a completed job.
3. Set a default expiry date for new links wherever possible.

In practice: what it looks like

In the example environment Nextcloud, you create a public link via the Share tab of a file. Under Modify you'll find the permissions (View only or Allow editing), and under Advanced settings the password, expiry date, Hide download, a note for the recipient, and Limit downloads. With Stop sharing you revoke the link immediately. If you share via an email address, Nextcloud sends each recipient their own link, which you can revoke per person. For incoming deliveries, there's the file request, with its own folder per client, password and expiry date. In Euro-Office you share documents via the same kind of links; the manual recommends only giving editing rights if that's really necessary. Other cloud storage works similarly, although the buttons are named differently and some options (such as a download limit) aren't available everywhere.

Summary

• Choose the most restricted way of sharing that works: internal, personal, and only as a last resort a public link.
• A public link works for anyone who has it; give it a password (via a different channel), an expiry date and view-only rights.
• Share the file, not the folder; use a file request if someone needs to deliver something to you.
• Don't send sensitive data as an ordinary attachment, and only share what the other person really needs.
• Regularly tidy up old links and external access.

Quiz

Exercise

Exercise A7.3: Assess the share link. You'll be given a series of situations with the settings of a share link: what's being shared, with whom, with what permissions, whether it has a password and expiry date, and how the password is sent. Assess for each situation whether it's fine, could be better, or shouldn't be done that way, and choose the most important improvement. The program checks your answer and gives an explanation for each situation.

Further reading

The steps in the WebOké articles apply to the WebOké environment; with other providers it works similarly.

• Nextcloud manual 5.2: Creating a public link: viewing, editing, password, expiration date and download limit
• Nextcloud manual 5.4: Sharing by email with someone without an account
• Nextcloud manual 16.5: Have a client submit files with a password-protected file request with an expiry date
• Euro-Office guide 9.3: Password and expiration date on a link
• Euro-Office guide 9.5: Sharing with someone outside your organisation