What does it mean when the Sophos error message "Virus Scan Failed: File Encrypted" is received?

Issue

What does it mean when the Sophos error message "Virus Scan Failed: File Encrypted" is received?

Solution

There are two possible meanings for this error message.

• Sophos cannot scan encrypted, or password protected files. To secure password protected files, MS Office and many other programs use encryption. Password protected files, even if not otherwise encrypted, also cannot be scanned successfully by Sophos (or other antivirus software). If such scanning were possible it would indicate the encryption was not sufficiently secure.
• Other antivirus software cannot scan encrypted, or password protected files successfully.

Sophos announces that it has delivered an unscanned file.

If the particular email that received this warning message contains attachments, try scanning the attachments on the desktop.

Some desktop applications such as WinZip and Microsoft Office 2000 support having desktop antivirus software act as plug-ins to scan files upon decompression or opening.

If using Microsoft Office, set the macro security settings to the appropriate security level to protect against any malicious macro viruses contained in a password-protected file.

If possible, an administrator may choose to have the Sophos software quarantine not only the files that are found to be infected, but also to quarantine files where scanning failed.

Note the following:

• Encrypted files cannot be scanned without first decrypting them, whether scanned on a Mirapoint appliance or on the desktop (PC, Mac, workstation, etc.). If scanning of encrypted files were possible, it would mean the encryption was not sufficiently secure.
• Password protected files are normally encrypted to prevent reading file contents using a hex editor. Therefore, such files cannot be scanned without first using the password to open the file.
• Mirapoint scans encrypted MS office files up to and including Microsoft Office 2000.
• If you want to suppress scan failure warning messages, Mirapoint offers the E4_SophosDA patch.