2FA for secure file sharing means access does not depend on a link or password alone. A second, A secure download link does not automatically prove that the right person is accessing a file. Two-factor authentication and other forms of recipient verification add an additional control. This reduces the likelihood that a forwarded link, misdirected email or stolen credential provides immediate access to confidential information.
Not every verification method offers the same level of protection. An email code, PIN, SMS code, authenticator app and phishing-resistant MFA each address different risks. The appropriate method depends on the sensitivity of the information, the type of recipient and the potential impact of unauthorised access.
In brief
2FA for secure file sharing means that access does not depend solely on a link or password. The recipient must complete an additional verification step before the file becomes available.
- A lower risk of misuse when links are forwarded or sent to the wrong address.
- Additional protection when a password or other access method is compromised.
- Different verification levels for different information classifications.
- Greater control over who can access information and for how long.
- Better evidence of control when verification is combined with access policies and logging.
2FA is not a complete security solution in itself. It is most effective when combined with appropriate permissions, limited availability, revocable access and a reliable audit trail.
Thijs van der Linden, COO of Msafe, wrote our first article on 2FA for file sharing in 2023. For this update, we asked him why the topic still matters so much.
“With customers, we kept seeing the same pattern. They had secured their own environment well, including MFA for employees. But as soon as a file left the organisation, security depended on a single link in an email. Whoever has the link has the file. Emails get forwarded, end up in shared mailboxes or are intercepted through a compromised account on the recipient’s side, or the sender accidentally uses the wrong email address. So the most sensitive step in the process, data leaving the organisation, was often the least protected.”
Thijs van der Linden, COO of Msafe
What is 2FA in secure file sharing?
Two-factor authentication, commonly abbreviated to 2FA, uses two independent factors to verify access. Authentication factors generally fall into three categories: something you know, something you have and something you are.
- Something you know, such as a password or PIN.
- Something you have, such as a phone, authenticator app or security key.
- Something you are, such as a fingerprint or facial recognition.
True 2FA combines factors from different categories. A password and a PIN, for example, are two separate steps, but both belong to the ‘something you know’ category. Technically, this is therefore not always genuine two-factor authentication.
In external file sharing, 2FA is frequently used more broadly for an additional recipient check. Recipient verification is a more accurate umbrella term. See the guidance from the Dutch National Cyber Security Centre for more information about identification, authentication and authorisation.
Why does external file sharing require additional verification?
Employees commonly access internal systems through a corporate account, Single Sign-On, a managed device and centrally enforced security policies. These safeguards are often unavailable when files are shared with customers, suppliers and other external recipients.
- An email address is entered incorrectly or completed incorrectly by the email application.
- The intended recipient forwards the download link to an unauthorised colleague.
- An attacker gains access to the recipient’s email account.
- A password or verification code is obtained through phishing.
- A previously trusted recipient no longer has a legitimate reason to retain access.
Possession of a link only proves that someone has obtained the URL. It does not prove who that person is or whether they should remain authorised to access the information. Additional verification reduces this risk.
“What goes wrong most often is not a sophisticated hack. It is a link ending up with the wrong person: a typo in the email address, autocomplete picking the wrong ‘John’, or a recipient forwarding the email to a colleague or a private address. A plain download link cannot see who clicks it. An anonymised example: an HR department sent a job offer to the wrong email address. With 2FA on the recipient’s side, that would have been a mistake without consequences, because the wrong recipient does not have the code. Without 2FA, it was a data breach with a reporting obligation.”
Thijs van der Linden, COO of Msafe
What is the difference between 2FA, MFA and recipient verification?
Two-step verification
The user completes two checks. These checks do not necessarily use two independent authentication factor categories.
Two-factor authentication
The user proves access using two independent factors, such as a password and an authenticator app.
Multi-factor authentication
MFA uses two or more independent authentication factors. Two-factor authentication is therefore a form of MFA.
Recipient verification
Recipient verification is the broader process of checking whether someone attempting to open a shared file meets the access conditions defined by the sender. This can involve genuine 2FA, but it can also use an SMS code, PIN or another verification step. Authentication checks access credentials; authorisation determines which files and actions are available.
Which verification method is appropriate for which risk?
Not every additional step provides the same level of assurance. The simplest method is therefore not automatically suitable for every type of information.
| Method | Primarily protects against | Main limitation | Appropriate use |
| Download link only | Access without the unique URL | The link can be forwarded | Non-confidential information |
| Email code | Use of a copied link outside the mailbox | Link and code may be accessible in the same mailbox | Occasional low-risk transfers |
| PIN via separate channel | Misuse of the link alone | Depends on how the PIN is communicated and managed | Known recipient and limited risk |
| SMS verification | Use of the link or password alone | Phishing, SIM swapping and number takeover | External recipients and medium risk |
| Authenticator app | Password theft and telecom-related attacks | One-time codes can still be phished | Returning users and established partners |
| Passkey/security key | Credential phishing | Registration and device management | Administration and high-risk access |
NIST does not consider SMS and similar out-of-band methods to be phishing-resistant. For higher-risk applications, methods cryptographically bound to the legitimate service are more appropriate. See the current NIST Digital Identity Guidelines.
When is SMS verification appropriate?
SMS verification is easy to use and immediately available to most external recipients. Recipients do not need to install another application or complete an extensive account-registration process.
It can provide a practical additional barrier when sharing files with customers, suppliers and occasional guests. SMS is stronger than relying on a download link alone, but it should not be treated as the strongest available method for every high-risk scenario.
- The recipient’s telephone number has been obtained through a trusted process.
- The download link and verification code are delivered through separate channels.
- Access remains valid for a limited period.
- The sender can revoke access.
- The organisation’s information-classification policy permits SMS verification.
Administrators, privileged internal users and established partners accessing highly sensitive information should use stronger, preferably phishing-resistant MFA wherever possible.
“SMS is good enough for the vast majority of external exchanges. It works for every recipient without installing anything, and it fully covers the biggest risk: the wrong recipient. SMS has known weaknesses such as SIM swapping, but that is a targeted attack. For highly sensitive data, or for recipients you exchange files with on a regular basis, I recommend a stronger method such as an authenticator app. In practice, Msafe customers mostly choose SMS as the default. An authenticator app is mainly used where there is internet access but no mobile reception, such as in a data centre. My rule of thumb: the method should match the sensitivity of the file, not the strictest situation imaginable.”
Thijs van der Linden, COO of Msafe
A practical risk matrix for file sharing
Organisations can define a minimum verification level for each information classification.
| Situation | Risk | Appropriate verification | Additional controls |
| General document sent to a known recipient | Low | Email verification or PIN | Limited availability and revocable access |
| Contract, quotation or internal design | Medium | SMS or authenticator app | Logging, controlled permissions and short expiry |
| Personal or financial information | High | Strong MFA where practicable | Least privilege, active oversight and restricted access |
| Special-category data or critical OT information | Very high | Phishing-resistant MFA for persistent access | Strict authorisation, monitoring and periodic review |
| Administrator account | Very high | SSO with phishing-resistant MFA | RBAC, Conditional Access and access reviews |
This matrix is a starting point. The final decision must reflect the organisation’s own risk assessment, information classification, contractual requirements and legal obligations.
Setting a 2FA policy for external recipients
A 2FA policy for external recipients defines which verification is required for which type of information, who decides, and how it is enforced in practice. A good policy includes at least:
- Information levels, such as public, internal, confidential and strictly confidential, with a verification requirement for each level.
- An owner: the security officer or CISO.
- The right people at the table: the privacy officer or DPO for the GDPR side, IT for configuration and rollout, and business users such as HR, finance and legal.
- Default settings in the tool, so employees do not have to think about it for every message.
- A usability check: a threshold that is too high leads to frustration and workarounds.
“Start with the data, not the technology. What information do you share with external parties, and how sensitive is it? Make that concrete in a number of levels and link a verification requirement to each level. Make sure someone from the business is at the table too, such as HR, finance or legal. They are the people who use it every day. If they are not involved, you end up with a policy that looks right on paper but is bypassed in practice. Then set it as the default in the tool, so employees do not have to think about it. Make sure it is effective, but also workable.”
Thijs van der Linden, COO of Msafe
Make the secure route the easiest one
A policy only works if employees follow it. That works best when the secure route is also the fastest, for example by sharing directly from Outlook with the Msafe Connector.
“Any security measure that creates too much friction will be bypassed. Then you get WeTransfer or a regular attachment after all. That is why the secure route has to be the easiest route. In concrete terms: sending from Outlook instead of a separate portal, verification applied automatically based on policy instead of chosen per message, and a code that reaches the recipient within seconds. Do not just ban the alternatives, make them unnecessary. And measure it: if a lot still goes through consumer services, that is a sign your tool creates too much friction, not that your employees are unwilling.”
Thijs van der Linden, COO of Msafe
One piece of advice for the CISO
“Make recipient verification the default, not the exception. Switch it on by default for all external exchanges of confidential information, so an employee has to consciously choose not to use it, instead of having to remember to use it. One setting with a big impact, and immediately demonstrable.”
Thijs van der Linden, COO of Msafe
Why 2FA alone is not enough
2FA reduces the risk that a single stolen or forwarded access method provides immediate access. It does not prevent every data breach.
- An authorised recipient may save or forward a local copy.
- A user may be assigned unnecessarily broad permissions.
- Malware may operate on the device of an authorised user.
- A file may remain available longer than necessary.
- A recipient may deliberately share their access method.
Recipient verification should therefore be combined with role-based permissions, predefined expiry, revocable access, logging, periodic reviews and clear recovery procedures.
Combining secure defaults, controlled processes and usable evidence is central to compliance by design in secure file sharing.
How does Msafe support secure recipient verification?
With Msafe Secure File Transfer, organisations can align the verification method with the recipient and the risk associated with the transfer.
External recipients
Depending on the applicable policy and configuration, guest access can be protected with 2FA or a PIN. Msafe supports SMS and authenticator apps for two-factor authentication. External recipients do not always require a full user account. This adds assurance without requiring every occasional recipient to complete an extensive onboarding process.
Internal users
Internal users can be centrally managed using Microsoft Entra ID, Single Sign-On and SCIM provisioning. Access can be updated when an employee joins, changes roles or leaves the organisation.
“With SSO, employees sign in with their existing Microsoft account. The MFA and Conditional Access policies the organisation already has then automatically apply to Msafe as well. There is no separate password to forget or leak. SCIM handles the lifecycle: when someone is created in Entra ID, added to a group or marked as having left, the Msafe account is automatically created, updated or blocked. Administrators mainly notice that work disappears. That is exactly what an auditor wants to see: demonstrable access management from a single source.”
Thijs van der Linden, COO of Msafe
Control after sending
Within Msafe, recipient verification can be combined with roles, access permissions, automatic expiry, revocation, retention policies and an audit trail of relevant events.
The audit trail records relevant events within Msafe. It does not necessarily prove who was physically operating a device, nor does it provide complete control over a file after it has been downloaded outside the platform. These limitations should form part of a reliable risk assessment.
Implementing 2FA for file sharing in six steps
1. Classify the information
Distinguish between public, internal, confidential and highly sensitive files. Determine the potential impact of unauthorised access.
2. Identify the type of recipient
Separate employees, established partners, known customers and occasional guests. Each requires a different balance between assurance and usability.
3. Define a minimum for each information class
Document when email verification or a PIN is sufficient and when SMS, an authenticator app or phishing-resistant MFA is required.
4. Add complementary controls
Configure permissions, expiry, revocation, retention and logging. Use secure defaults so employees do not have to make every security decision themselves.
5. Test exceptional situations
Test an incorrect email address, a forwarded link, a changed telephone number, recovery and employee offboarding.
6. Review effectiveness periodically
Assess failed verification attempts, exceptions, user friction and audit information. Update policies when risks or capabilities change.
What do GDPR, NIS2 and the Dutch Cybersecurity Act mean for 2FA?
GDPR does not prescribe one specific form of 2FA for every file transfer. Organisations must implement appropriate technical and organisational measures based on the risks associated with the processing.
The official NIS2 Directive identifies multi-factor authentication or continuous authentication, where appropriate, as part of a broader risk-based set of cybersecurity measures.
The Dutch Cybersecurity Act has been in force since 15 August 2026 and implements NIS2 in the Netherlands. Organisations within its scope must take appropriate and proportionate measures. See the official Dutch government announcement.
2FA does not automatically make file sharing compliant. Demonstrable compliance also requires documented policies, appropriate authorisation, retention periods, logging, evaluation and evidence that the selected controls operate effectively.
For a related decision on collaboration and external exchange, see SharePoint versus Secure File Transfer.
“The Dutch Cyberbeveiligingswet does not literally say ‘use 2FA for file sharing’, but the duty of care requires appropriate and proportionate measures. NIS2 explicitly mentions multi-factor authentication and supply chain security. Sending sensitive data to external parties without verifying who receives it is hard to justify as appropriate. What is new is that the board is accountable: it must approve the measures and oversee them. Organisations must be able to show that there is a policy, that it is technically enforced, and who received and verified what, and when. An audit trail per transfer is then not a luxury but your evidence for the regulator. And in an incident, it helps you determine the impact within the reporting deadlines.”
Thijs van der Linden, COO of Msafe
Checklist for CISOs, IT and privacy teams
- Is it documented when additional recipient verification is mandatory?
- Is the distinction between genuine 2FA and two-step verification clear?
- Has a minimum protection level been defined for each information class?
- Can access be revoked immediately and expire automatically?
- Are administrators protected more strongly than occasional guests?
- Are telephone-number changes, recovery procedures and exceptions secured?
- Can the organisation reconstruct relevant access events and changes?
- Are settings and exceptions reviewed periodically?
Frequently asked questions about 2FA and file sharing
Is an email code genuine 2FA?
Not when the download link and verification code are accessible through the same mailbox. The code may protect against someone who only has the link, but adds little protection if the mailbox itself is compromised.
Is a PIN the same as 2FA?
Not automatically. A PIN is generally a ‘something you know’ factor. Combined with a password, it represents two steps from the same category. It can still provide a useful additional control when communicated through a separate channel.
Is SMS-based 2FA secure enough?
SMS is stronger than a link or password alone, but it is not phishing-resistant. Its suitability depends on the files, recipient, threat scenario and complementary controls.
Does 2FA prevent phishing?
Not every form does. SMS and authenticator-app codes can be captured through a convincing phishing site. Passkeys and security keys offer greater resistance.
Does an external recipient need a Msafe account?
Not always. Depending on policy and configuration, guest access can use 2FA or a PIN without requiring every recipient to have a full account.
Can access be revoked after sending?
Access through the platform can be revoked while the file remains available there. A local copy that has already been downloaded generally cannot be remotely deleted.
Does 2FA make file sharing compliant?
No. Compliance also depends on purpose and legal basis, risk assessment, permissions, retention periods, contracts, logging and demonstrable operation of the overall process.
Select verification that matches the risk
The strongest verification method is not automatically the most appropriate method for every recipient. Excessive friction can lead to delays, support requests or insecure workarounds. Insufficient verification may leave confidential information inadequately protected.
Balance assurance and usability for each information flow. Distinguish between occasional guests, established partners, employees and administrators. Always combine recipient verification with permissions, limited availability, revocable access and logging.
Would you like to determine which verification methods are appropriate for your external information flows? Request a demonstration or proof of concept and test Msafe using a representative file, a genuine external recipient and your own requirements for access control and demonstrable evidence.
