Policies - Malware Bypass Configuration

This article is to provide guidelines on how the Suspected Malware policies detect and prevent zero-day malware (malware where specific antivirus software signatures aren't yet available) and spam outbreaks. These checks provide protection against previously unknown threats using deep-level anomaly detection and trending. Suspected Malware Bypass policies allow you to configure certain mail flows to bypass these default malware checks.
 

A Suspected Malware Bypass policy must only be configured if regular attachments are being blocked that need to be allowed through. Bypassing malware checks in other circumstances can result in a new virus outbreak going undetected while signatures are being updated. Messages containing compressed (.ZIP) attachments that themselves contain an .EXE, .COM, .PIF, .SCR, .CPL, or .MSI file, are placed in the hold queue and marked as suspected malware. The intended recipient is sent a notification and must ask an administrator to release the message. Encrypted compressed (.ZIP) files cannot be checked by a suspected malware policy. For this scenario, we recommend using Configuring Attachment Management Policies. Messages placed in the hold queue due to a Suspicious Message Structure indicate that they have not been correctly structured.

Configuring a Suspected Malware Bypass Policy

To configure a Suspected Malware Bypass policy:

1. Log in to the Mimecast Administration Console.
2. Select the Policies | Gateway Policies menu item.
3. Click on Suspected Malware Bypass.
4. Either select the:

• • • Policy to be changed.
    • New Policy button to create a policy.

5.   Complete the Options section as required:

Field / Option	Description
Policy Narrative	Provide a description of the policy to allow you to easily identify it in the future.
Select Option	Select whether to hold or ignore suspected malware.

6. Complete the Emails From and Emails To sections as required:

Field / Option	Description
Addresses Based On	Specify the email address characteristics on which the policy is based. This option is only available in the Emails From section. The options are: The Return Address (Mail Envelope From): This default setting applies the policy to the SMTP address match based on the message's envelope or true address (i.e., the address used during SMTP transmission). The Message From Address (Message Header From):  Applies the policy based on the masked address used in the message's header. Both: Applies the policy based on either the Mail Envelope From or the Message Header From whichever matches. If both match the specified value, the Message Header From is used.
Applies From / To	Specify the Sender characteristics on which the policy is based. For multiple policies, you should apply them from the most to the least specific. The options are: Everyone: Includes all email users (i.e., internal and external). This option is only available in the Emails From section. Internal Address: Includes only internal organization addresses. External Address: Includes only external organization addresses. This option is only available in the Emails From section. Email Domain: Enables you to specify a domain name to which this policy is applied. The domain name is entered in the Specifically field. Address Groups: Enables you to specify a directory or local group. If this option is selected, click on the Lookup button to select a group from the Profile Group field. Once a group has been selected, you can click on the Show Location field to display the group's path. Address Attributes: Enables you to specify a predefined Attribute. The attribute is selected from the Where Attribute drop-down list. Once the Attribute is specified, an attribute value must be entered in the Is Equal To field. This can only be used if attributes have been configured for user accounts. Individual Email Address: Enables you to specify an SMTP address. The email address is entered in the Specifically field.

7. Complete the Validity section as required:

Field / Option	Description
Enable / Disable	Use this to enable (default) or disable a policy. If a date range has been specified, the policy will automatically be disabled when the end of the configured date range is reached.
Set Policy as Perpetual	If the policy's date range has no end date, this field displays Always On, meaning that the policy never expires.
Date Range	Use this field to specify a start and/or end date for the policy. If the Eternal option is selected, no date is required.
Policy Override	This overrides the default order in which policies are applied. If there are multiple applicable policies, this policy is applied first unless more specific policies of the same type are configured with an override.
Bi-Directional	If selected, the policy is applied when the policy's recipient is the sender, and the sender is the recipient.
Source IP Ranges (n.n.n.n/x)	Enter any required Source IP Ranges for the policy. These only apply if the source IP address used to transmit the message data falls inside or matches the range(s) configured. IP ranges should be entered in CIDR notation.

8. Click on the Save and Exit button.

See Also...

• • • Policy Specificity