Is a password-protected excel file considered secure versus encrypted file or email

Question

I understand that encryption is the highest form of security for document/data storage.

While a password-protected document is more secure than one without password protection, if the document is sent via email that is NOT encrypted, is the document considered secure?

Answer 1

It's really broad to ask about whether a document is considered "secure". Something that is "secure" enough for me, sending a love poem to my girlfriend, is not "secure" enough for Obama, sending a love poem to Putin.

As Alexander O'Mara mentioned in a comment, there are different ways of setting a password on a file.

Excel gives you several ways to protect a workbook.

You can require a password to open it, a password to change data, and a password for changing the file's structure—adding, deleting, or hiding worksheets.

You can also set a password in Backstage view that encrypts your workbook.

Remember, though, that this type of protection doesn't always encrypt your data - only the encrypting password created in Backstage view does that. Users can still use third-party tools to read data that isn't encrypted. (from here )

So it seems that simply password protecting an excel file would not be very "secure", as someone might still be able to view the data with a third party tool.

That said, assuming you want edit protection, it again depends what you later do with the password, or how you would transmit it to the person later using it.

Answer 2

Excel is totally insecure as it does not take long to find a password by brute force methods. For example in vba:

Sub PasswordBreaker()
 'Breaks worksheet password protection.
 Dim i As Integer, j As Integer, k As Integer
 Dim l As Integer, m As Integer, n As Integer
 Dim i1 As Integer, i2 As Integer, i3 As Integer
 Dim i4 As Integer, i5 As Integer, i6 As Integer
 On Error Resume Next
 For i = 65 To 66: For j = 65 To 66: For k = 65 To 66
  For l = 65 To 66: For m = 65 To 66: For i1 = 65 To 66
   For i2 = 65 To 66: For i3 = 65 To 66: For i4 = 65 To 66
    For i5 = 65 To 66: For i6 = 65 To 66: For n = 32 To 126
     ActiveSheet.Unprotect Chr(i) & Chr(j) & Chr(k) & _
       Chr(l) & Chr(m) & Chr(i1) & Chr(i2) & Chr(i3) & _
       Chr(i4) & Chr(i5) & Chr(i6) & Chr(n)
     If ActiveSheet.ProtectContents = False Then
       MsgBox "One usable password is " & Chr(i) & Chr(j) & _
        Chr(k) & Chr(l) & Chr(m) & Chr(i1) & Chr(i2) & _
        Chr(i3) & Chr(i4) & Chr(i5) & Chr(i6) & Chr(n)
       Exit Sub
     End If
     Next: Next: Next: Next: Next: Next
  Next: Next: Next: Next: Next: Next
End Sub