This article contains information on using MD5 hash checksums in Mimecast to prevent confidential documents from leaving your environment, including steps to add MD5 hashes to content examination definitions, configure policies, and utilize regular expressions for enhanced data security.
Adding a File MD5 Hash to a Definition
To add a File MD5 Hash to a definition:
- Log in to the Mimecast Administration Console.
- Navigate to Policies | Gateway Policies.
- Hover over the Definitions button. A list of the definition types is displayed.
- Select the Content Examinations definition type from the list. The list of definitions is displayed.
- Either click on the:
-
-
- Definition to be changed.
- New Content Definition button.
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- Click on the Insert button.
- Click on the File MD5 Hash menu item.
- Complete the Policy Definition dialog as follows:
| Field / Option | Description |
|---|---|
| Line Score | Specify a value for the MD5 hash compared to the Activation Score in the definition. |
| Append | If selected, the MD5 hash is placed at the bottom of the Word/Phrase Match List. If unselected, it is placed at the top of the list. |
| Attachment MD5 Hash | Specify an automatically generated MD5 hash unique to the file specified in the New File Upload field. This is used to prevent confidential documents from leaving your environment. By uploading the document, an MD5 hash is generated. If we detect the hash in a message, the action specified in the definition is taken. |
| New File Upload | Click on the Browse button to select the required file. |
| Comment | Add any notes that refer to the MD5 hash. These are only displayed in the Word/Phrase Match List field prefixed by a hash symbol (#). All comments are ignored when examining messages for matches. |
- Click on the Save and Exit button.
- Repeat steps 7 - 10 to add any additional File MD5 Hash to the definition.
MD5 Hash Checksum
Checksums are generated from the Insert menu item inside a Content Examination definition. See Using the Insert Menu.
Activation score = 1
| Word / Phrase Match List | Email Content Required to Trigger Definition |
|---|---|
| #1 hash 00C9443961BC9131FE96D580AB29CE59 mimecast.xls - (30208 Bytes) | The mimecast.xls file must be present in the email. |
Regular Expressions (Text Matches)
Activation score = 4
| Word / Phrase Match List | Email Content Required to Trigger Definition |
|---|---|
| 1 regex [bcr]at 10 regex DOB (date of birth) (?:[\W\D\S])?\s?\d{1,2}(?:\/|\.)\d{1,2}(?:\/|\.)\d{2,4}\b |
4 occurrences of words ending in ‘at’, such as ‘bat’, ‘rat’, ‘cat’ etc. OR 1 occurrence of a reference to a Date of birth in the email with the format: Date of birth: MM|DD/MM|DD/YY|YYYY For more Date Formats: Month Day Year: (([0-1][0-2])|([0][1-9]|[1][1-2]))(.| |/|-)(([0-2][0-9])|([3][0-1]))(.| |/|-)(([1][9][0-9][0-9])|([2][0][0-9][0-9])|(/d{2})) Day Month Year: (([0-2][0-9])|([3][0-1]))(.| |/|-)(([0-1][0-2])|([0][1-9]|[1][1-2]))(.| |/|-)(([1][9][0-9][0-9])|([2][0][0-9][0-9])|(/d{2})) Year Month Day: (([1][9][0-9][0-9])|([2][0][0-9][0-9])|(/d{2}))(.| |/|-)(([0-1][0-2])|([0][1-9]|[1][1-2]))(.| |/|-)(([0-2][0-9])|([3][0-1])) Year Day Month: (([1][9][0-9][0-9])|([2][0][0-9][0-9])|(/d{2}))(.| |/|-)(([0-2][0-9])|([3][0-1]))(.| |/|-)(([0-1][0-2])|([0][1-9]|[1][1-2])) |
| 5 regex (pre-|post-) operative | 1 occurrence of ‘pre-operative’ OR ‘post-operative’ |
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