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Mimecast Email Security

Overview

A secure email gateway to block spam, viruses, and malware.

Warning

Important note - This format is currently in beta. We highly value your feedback to improve its performance.

The following Sekoia.io built-in rules match the intake Mimecast Email Security [BETA]. This documentation is updated automatically and is based solely on the fields used by the intake which are checked against our rules. This means that some rules will be listed but might not be relevant with the intake.

SEKOIA.IO x Mimecast Email Security [BETA] on ATT&CK Navigator

Cryptomining

Detection of domain names potentially related to cryptomining activities.

  • Effort: master
Dynamic DNS Contacted

Detect communication with dynamic dns domain. This kind of domain is often used by attackers. This rule can trigger false positive in non-controlled environment because dynamic dns is not always malicious.

  • Effort: master
Exfiltration Domain

Detects traffic toward a domain flagged as a possible exfiltration vector.

  • Effort: master
Remote Access Tool Domain

Detects traffic toward a domain flagged as a Remote Administration Tool (RAT).

  • Effort: master
SEKOIA.IO Intelligence Feed

Detect threats based on indicators of compromise (IOCs) collected by SEKOIA's Threat and Detection Research team.

  • Effort: elementary
Sekoia.io EICAR Detection

Detects observables in Sekoia.io CTI tagged as EICAR, which are fake samples meant to test detection.

  • Effort: master
TOR Usage Generic Rule

Detects TOR usage globally, whether the IP is a destination or source. TOR is short for The Onion Router, and it gets its name from how it works. TOR intercepts the network traffic from one or more apps on user’s computer, usually the user web browser, and shuffles it through a number of randomly-chosen computers before passing it on to its destination. This disguises user location, and makes it harder for servers to pick him/her out on repeat visits, or to tie together separate visits to different sites, this making tracking and surveillance more difficult. Before a network packet starts its journey, user’s computer chooses a random list of relays and repeatedly encrypts the data in multiple layers, like an onion. Each relay knows only enough to strip off the outermost layer of encryption, before passing what’s left on to the next relay in the list.

  • Effort: master

Event Categories

The following table lists the data source offered by this integration.

Data Source Description
Email gateway Inbound, outbound and internal logs for messages

In details, the following table denotes the type of events produced by this integration.

Name Values
Kind ``
Category email
Type denied, info

Event Samples

Find below few samples of events and how they are normalized by Sekoia.io.

{
    "message": "{\"aggregateId\": \"vC80NNxvOWKkBPnzSs04FA_1715699686\", \"processingId\": \"PGZfGuxEAu_kE-nGy1sjThBr5EYbm1ZcDKg-vXbRHLA_1715699686\", \"accountId\": \"CDE22A102\", \"timestamp\": 1715699697146, \"senderEnvelope\": \"newsletter@stub.com\", \"recipients\": \"neo@gmail.fr\", \"direction\": \"Inbound\", \"type\": \"journal\", \"subtype\": null, \"_offset\": 105760, \"_partition\": 137}",
    "event": {
        "category": [
            "email"
        ],
        "dataset": "journal",
        "provider": "Mimecast",
        "type": [
            "info"
        ]
    },
    "@timestamp": "2024-05-14T15:14:57.146000Z",
    "email": {
        "direction": "Inbound",
        "from": {
            "address": [
                "newsletter@stub.com"
            ]
        },
        "to": {
            "address": [
                "neo@gmail.fr"
            ]
        }
    },
    "mimecast": {
        "siem": {
            "aggregate_id": "vC80NNxvOWKkBPnzSs04FA_1715699686",
            "processing_id": "PGZfGuxEAu_kE-nGy1sjThBr5EYbm1ZcDKg-vXbRHLA_1715699686"
        }
    }
}
{
    "message": "{\"aggregateId\": \"J5JwSy0HNvG7AvCg1sgDvQ_1715708284\", \"processingId\": \"hP5f7mBanAVkWJWfh4vYvca3zOi9I3jROBmH3Z_Kysk_1715708284\", \"accountId\": \"CDE22A102\", \"action\": \"Hld\", \"timestamp\": 1715708287466, \"senderEnvelope\": \"john.doe015@gmail.com\", \"messageId\": \"<CAF7=BmDb+6qHo+J5EB9oH+S4ncJOfEMsUYAEirX4MRZRJX+esw@mail.gmail.com>\", \"subject\": \"Moderate\", \"holdReason\": \"Spm\", \"totalSizeAttachments\": \"0\", \"numberAttachments\": \"0\", \"attachments\": null, \"emailSize\": \"3466\", \"type\": \"process\", \"subtype\": \"Hld\", \"_offset\": 105825, \"_partition\": 137}",
    "event": {
        "action": "Hld",
        "category": [
            "email"
        ],
        "dataset": "process",
        "provider": "Mimecast",
        "type": [
            "info"
        ]
    },
    "@timestamp": "2024-05-14T17:38:07.466000Z",
    "email": {
        "from": {
            "address": [
                "john.doe015@gmail.com"
            ]
        },
        "message_id": "CAF7=BmDb+6qHo+J5EB9oH+S4ncJOfEMsUYAEirX4MRZRJX+esw@mail.gmail.com",
        "to": {
            "address": [
                "null"
            ]
        }
    },
    "mimecast": {
        "siem": {
            "aggregate_id": "J5JwSy0HNvG7AvCg1sgDvQ_1715708284",
            "hold_reason": "Spm",
            "processing_id": "hP5f7mBanAVkWJWfh4vYvca3zOi9I3jROBmH3Z_Kysk_1715708284"
        }
    }
}
{
    "message": "{\"processingId\": \"processingId\", \"aggregateId\": \"aggregateId\", \"numberAttachments\": \"2\", \"attachments\": \"tpsreport.doc\", \"subject\": \"siem_process - email subject line\", \"senderEnvelope\": \"auser@mimecast.com\", \"messageId\": \"messageId\", \"eventType\": \"process\", \"accountId\": \"C0A0\", \"action\": \"Allow\", \"holdReason\": null, \"subType\": \"Allow\", \"totalSizeAttachments\": \"642\", \"timestamp\": 1689685338609, \"emailSize\": \"56422\"}",
    "event": {
        "action": "Allow",
        "category": [
            "email"
        ],
        "dataset": "process",
        "provider": "Mimecast",
        "type": [
            "info"
        ]
    },
    "@timestamp": "2023-07-18T13:02:18.609000Z",
    "email": {
        "attachments": [
            {
                "file": {
                    "name": "tpsreport.doc"
                }
            }
        ],
        "from": {
            "address": [
                "auser@mimecast.com"
            ]
        },
        "message_id": "messageId",
        "to": {
            "address": [
                "null"
            ]
        }
    },
    "mimecast": {
        "siem": {
            "aggregate_id": "aggregateId",
            "processing_id": "processingId"
        }
    }
}
{
    "message": "{\"aggregateId\": \"J5JwSy0HNvG7AvCg1sgDvQ_1715708284\", \"processingId\": \"hP5f7mBanAVkWJWfh4vYvca3zOi9I3jROBmH3Z_Kysk_1715708284\", \"accountId\": \"CDE22A102\", \"timestamp\": 1715708286579, \"action\": \"Acc\", \"senderEnvelope\": \"john.doe@gmail.com\", \"messageId\": \"<CAF7=BmDb+6qHo+J5EB9oH+S4ncJOfEMsUYAAarX4MRZRJX+esw@mail.gmail.com>\", \"subject\": \"Moderate\", \"recipients\": \"admin@mcfr2.pro\", \"senderIp\": \"209.123.123.123\", \"rejectionType\": null, \"rejectionCode\": null, \"direction\": \"Inbound\", \"numberAttachments\": \"0\", \"senderHeader\": \"john.doe@gmail.com\", \"rejectionInfo\": null, \"tlsVersion\": \"TLSv1.3\", \"tlsCipher\": \"TLS_AES_256_GCM_SHA384\", \"spamInfo\": \"[]\", \"spamProcessingDetail\": \"{\\\"spf\\\":{\\\"allow\\\":true,\\\"info\\\":\\\"ALLOW\\\"},\\\"dkim\\\":{\\\"allow\\\":true,\\\"info\\\":\\\"ALLOW\\\"},\\\"dmarc\\\":{\\\"allow\\\":true,\\\"info\\\":\\\"ALLOW\\\"}}\", \"virusFound\": null, \"type\": \"receipt\", \"subtype\": \"Acc\", \"_offset\": 105826, \"_partition\": 137}",
    "event": {
        "action": "Acc",
        "category": [
            "email"
        ],
        "dataset": "receipt",
        "provider": "Mimecast",
        "type": [
            "info"
        ]
    },
    "@timestamp": "2024-05-14T17:38:06.579000Z",
    "email": {
        "direction": "Inbound",
        "from": {
            "address": [
                "john.doe@gmail.com"
            ]
        },
        "message_id": "CAF7=BmDb+6qHo+J5EB9oH+S4ncJOfEMsUYAAarX4MRZRJX+esw@mail.gmail.com",
        "to": {
            "address": [
                "admin@mcfr2.pro"
            ]
        }
    },
    "mimecast": {
        "siem": {
            "aggregate_id": "J5JwSy0HNvG7AvCg1sgDvQ_1715708284",
            "processing_id": "hP5f7mBanAVkWJWfh4vYvca3zOi9I3jROBmH3Z_Kysk_1715708284"
        }
    },
    "related": {
        "ip": [
            "209.123.123.123"
        ]
    },
    "source": {
        "address": "209.123.123.123",
        "ip": "209.123.123.123"
    }
}

Extracted Fields

The following table lists the fields that are extracted, normalized under the ECS format, analyzed and indexed by the parser. It should be noted that infered fields are not listed.

Name Type Description
@timestamp date Date/time when the event originated.
destination.ip ip IP address of the destination.
email.attachments nested List of objects describing the attachments.
email.direction keyword Direction of the message.
email.from.address keyword The sender's email address.
email.message_id wildcard Value from the Message-ID header.
email.to.address keyword Email address of recipient
event.action keyword The action captured by the event.
event.category keyword Event category. The second categorization field in the hierarchy.
event.dataset keyword Name of the dataset.
event.provider keyword Source of the event.
event.type keyword Event type. The third categorization field in the hierarchy.
mimecast.siem.aggregate_id keyword Unique identifier that allows you to correlate/group related events.
mimecast.siem.delivered boolean If the email was delivered successfully or not.
mimecast.siem.delivery_errors keyword Information about any errors that occurred on the delivery attempt.
mimecast.siem.hold_reason keyword The reason the email was held for review (quarantined), if applicable.
mimecast.siem.processing_id keyword Unique identifier that allows you to correlate/group related events.
mimecast.siem.rejection.code number The rejection code issued if the email was rejected at the receipt stage.
mimecast.siem.rejection.info keyword The rejection information if the email was rejected at the receipt stage.
mimecast.siem.rejection.type keyword The rejection type if the email was rejected at the receipt stage.
mimecast.siem.virus_found keyword The name of the virus found on the email, if applicable.
source.ip ip IP address of the source.

Configure

Create API credentials

  1. Login to Mimecast Administration Console
  2. Navigate to Services | API and Platform Integrations
  3. Locate the following Mimecast API 2.0 tile and click on Generate Keys.
  4. After reading the Terms & Conditions, complete the I accept check box to enable the Next button to progress onto the next step.
  5. Complete the Application Details section.
  6. Please provide details for a Technical Point of Contact.
  7. Review the Summary information for the API application and click on Add if you are happy to proceed with creating the application.
  8. The wizard completes and displays a pop-up window including your Client ID and Client Secret key data.

Create your intake

  1. Go to the intake page and create a new intake from the Mimecast Email Security.
  2. Copy the associated Intake key

Pull your logs on Sekoia.io

Go to the Sekoia.io playbook page, and follow these steps:

  • Click on + PLAYBOOK button to create a new one
  • Select Create a playbook from scratch
  • Give it a name in the field Name
  • Open the left panel, click Mimecast then select the trigger [BETA] Fetch new email events from Mimecast
  • Click on Create

  • Create a Module configuration using your Client ID and Client Secret created on the How to create API credentials step. Name the module configuration as you wish

  • Create a Trigger configuration and Type the Intake key created on the previous step
  • Click on the Save button
  • Activate the playbook with the toggle button on the top right corner of the page

Enjoy your events on the Events page

Further Readings