Below you will find information on using the Sandbox Service in NoSpamProxy. For general information on how a cloud sandbox works, licensing or data protection, see Informationen zum NoSpamProxy Sandbox-Service (German only).
Since 2018, we strongly recommend NoSpamProxy customers to take a whitelisting approach to content filtering (see our article on email firewalls). This recommendation applies in particular to the use of the NoSpamProxy Sandbox service.
An example: Even if an “executable file for Windows” is supported by the sandbox, the question arises whether one wants to allow this potentially dangerous file type for one’s own company at all. In this case, it makes more sense to generally reject this file type and thus also save the upload to the sandbox.
If a file is classified as unsuspicious by the sandbox service, the respective email will be delivered.
Sandbox hash query
The retrieval of the hash values from the sandbox database can be carried out without restriction and without deduction of purchased licences. For this purpose, the corresponding check mark Query the sandbox if the attachments of inbound emails are known to be malicious must be ticked.
This check can be applied to all file types.
File uploads are limited to 20 files per user and month.
This value is the total value of permitted uploads; there is no strict user check. This means, for example, for a 50-user licence that the respective NoSpamProxy installation may upload 1000 files to the sandbox in one month. Costs may be incurred if the limit is exceeded.
To limit the sandbox check to individual file types, an additional content filter action should be created that is only applied to certain file types.
To enable uploading, the option Upload unknown files to the sandbox for analysis must be activated.
Supported file types
- Executable files
- Executable files for Windows
- Office – Word
- Office – Excel
- Office – PowerPoint
- Adobe Flash (SWF)
- Adobe Flash Video (FLV)
- Rich Text Format
- Rich Text Format with OLE objects
- PDF with URLs
- Archives and compressed files
- ZIP-compressed file
- GZIP-compressed file
- TAR archive
- GZIP-compressed TAR archive
- 7Zip-compressed file
- Scripts (Configuration via file names)
If a file has to be uploaded to the sandbox (sandbox upload), the email will not be accepted initially and temporarily rejected so that the sending email server delivers it again.
The temporary rejection is applied here because the analysis on the sandbox array takes a certain amount of time, but should be completed after a regular 5 minutes when a new delivery attempt is made.
This will result in a delivery delay for the respective emails which must be taken into account accordingly. We therefore recommend that you check exactly which files should really be sent to the sandbox. Note the following option if time-critical processes or mailboxes exist in your company:
- Is a sandbox hash query sufficient instead of a complete analysis (sandbox upload)?
- It is possible to create different actions in the content filter to configure different actions for a content filter entry for “Trusted emails” and “Untrusted emails” between a sandbox upload and a sandbox hash query.
- Office documents can be converted into a secure PDF document by NoSpamProxy Content Disarming if necessary.