How to send sensitive data by email
What is the main problem
Sending any kind of information via "standard" email, i.e. without end-to-end encryption (E2E), is in general insecure since all mail data can be read by attackers. Consider email as a electronic post card.
Important: Never send sensitive information in emails (neither in the subject/body nor as an unsecured attachment)
Unfortunately, to setup an E2E email is still challenging for the majority and annoying when you just want to send a single email to someone you do not correspond with regularly.
In case you want to send sensitive data (e.g. credit card, personal data, etc) via email it is much easier to store all these data in one or more file(s) and send them as an encrypted attachment.
Sending encrypted attachments
- If your data are already in a document (e.g. Word, Excel) you are done here. For other data just create a new TXT file and enter your data.
Locate the document(s) you would like to send in Windows File Explorer and right-click it. Click 7-Zip, then Add to archive... (see image).
Remark: 7-Zip is installed on all ISG managed Windows clients. User off self-managed/BOYD devices can download 7-Zip.
Within 7-Zip select the archive format and Encryption method as shown in the image. Furthermore enter a password for encryption, according to the following rules:
- Select a strong password, i.e. [a-z,A-Z,0-9] and at least 10 character long
- The password must be different to any other passwords you use (also to encrypted attachments you sent to other users)
- Keep in mind that the data in the encrypted archive can not be recovered with out this password
Create the archive by clicking on OK. If you have not changed the location the archive will be created in the same location as the original data.
Attached the encrypted and password-protected archive to your email and send it. Do not send the password with the same email!
- The best way to send the password is using a different communication channel and to send it plain, i.e. without any further information (like the purpose of the password). Here is a list of possible communication channel in decreasing order of their level of trust:
- in person
- by phone
via chat, WhatsApp, Signal etc.
- by a separate email
Receiving encrypted attachments
- Save the attached encrypted archive to the file system
Locate the archive in Windows File Explorer and right-click it. Click 7-Zip, then Extract Here (see image).
- Enter the valid password
Additional note for Linux users
7-Zip is also available on our managed Linux clients and for the major Linux distributions (package p7zip). On Ubuntu the default archive tool ark works as well.
- Encrypting an attachment
/usr/bin/7z a -t7z -mhe=on -p <archive>.7z <file>, (7z will prompt for the password automatically)
- Decrypting an attachment
/usr/bin/7z e <archive>.7z, (7z will prompt for the password automatically)