Why Email Attachments Are a Security Risk

Email attachments have been the standard way to share files for decades. But this convenience comes with significant security risks that most people don’t consider.

The Hidden Journey of an Email Attachment

When you attach a file to an email, you might think it goes directly to the recipient. In reality:

Primary Security Risks

1. No Encryption at Rest

While many email providers encrypt data in transit (between servers), most don’t encrypt emails at rest:

• Emails stored on servers are readable
• Backups may be unencrypted
• Administrator access is possible
• Legal requests can access stored emails

2. No Access Revocation

Once you send an attachment:

• You can’t delete it from the recipient’s inbox
• You can’t prevent forwarding
• You can’t track who actually accessed it
• The file exists forever unless manually deleted

3. Storage Persistence

Emails are rarely deleted:

• Most people never clean their inbox
• Automatic archiving preserves everything
• Backup systems retain copies for years
• Compliance requirements may mandate retention

4. Forwarding Risk

Your carefully secured attachment can be:

• Forwarded to unauthorized recipients
• CC’d accidentally to the wrong people
• Shared in reply-all disasters
• Included in automated forwarding rules

Real-World Scenarios

Scenario 1: The Forgotten Attachment

You email a client their completed tax return. Three years later, their email account is compromised. The attacker finds your attachment and now has full access to sensitive financial information.

Scenario 2: The Accidental Forward

You send a confidential contract to a client. They forward it to their business partner for review, not realizing it contains pricing you didn’t want disclosed. You have no idea this happened.

Scenario 3: The Ex-Employee

You emailed login credentials to an employee. They left the company two years ago but still have access to their personal email where those credentials sit in the archive.

Compliance Implications

Email attachments can violate compliance requirements:

HIPAA

• Requires encryption for PHI
• Requires access controls
• Requires audit trails
• Standard email fails all three

GDPR

• Requires appropriate security measures
• Requires data minimization
• Requires ability to delete data
• Email makes compliance difficult

PCI-DSS

• Prohibits emailing payment card data
• Requires encryption and access controls
• Email attachments don’t qualify

SOC 2

• Requires documented security controls
• Requires access management
• Email lacks necessary controls

Safer Alternatives

Secure File Sharing Services

Examples: Dropbox Business, Google Drive, OneDrive, Tresorit

Benefits:

• Encrypted storage
• Access controls
• Share links instead of files
• Revocable access
• Audit logs

Secure Client Portals

Examples: Persay, various industry-specific solutions

Benefits:

• Designed for sensitive data
• End-to-end encryption
• Automatic expiration
• Client-friendly interface

Encrypted Email Services

Examples: ProtonMail, Tutanota

Benefits:

• End-to-end encryption
• Self-destructing messages
• Zero-knowledge architecture

Making the Transition

For Your Team

1. Start with high-risk files - Implement secure sharing for the most sensitive documents first
2. Make it easy - Choose tools that integrate with existing workflows
3. Lead by example - Management should use secure methods visibly
4. Provide support - Help team members who struggle with new tools

For Clients

I was worried clients would push back on using a portal instead of email. Turns out, they appreciated it. Several mentioned it made them feel their data was being handled professionally.

Communication tips:

• Frame it as protection for them
• Provide clear instructions
• Offer technical support
• Be patient during transition

What If You Must Use Email Attachments?

Sometimes email is the only option. Minimize risk by:

1. Password-protect files (with real encryption, not just PDF passwords)
2. Send password separately via text or call
3. Minimize sensitive content where possible
4. Ask recipient to confirm receipt and delete from their inbox
5. Delete from your sent folder after confirmation

Conclusion

Email attachments are a legacy practice from a time before cybersecurity was a daily concern. While convenient, they create permanent, uncontrolled copies of your sensitive files across multiple systems.

Modern alternatives provide the convenience of sharing with the security your business—and your clients—deserve. The transition requires some effort, but the reduced risk and increased professionalism make it worthwhile.

Start by identifying your highest-risk attachments and implementing secure alternatives for those first.