GSuite Email Suspicious Attachment
Description
This search is to detect a suspicious attachment file extension in Gsuite email that may related to spear phishing attack. This file type is commonly used by malware to lure user to click on it to execute malicious code to compromised targetted machine. But this search can also catch some normal files related to this file type that maybe send by employee or network admin.
- Type: Anomaly
-
Product: Splunk Enterprise, Splunk Enterprise Security, Splunk Cloud
- Last Updated: 2021-08-16
- Author: Teoderick Contreras, Splunk
- ID: 6d663014-fe92-11eb-ab07-acde48001122
Annotations
ATT&CK
Kill Chain Phase
- Exploitation
NIST
CIS20
CVE
Search
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`gsuite_gmail` "attachment{}.file_extension_type" IN ("pl", "py", "rb", "sh", "bat", "exe", "dll", "cpl", "com", "js", "vbs", "ps1", "reg","swf", "cmd", "go")
| eval phase="plan"
| eval severity="medium"
| stats count min(_time) as firstTime max(_time) as lastTime values(attachment{}.file_extension_type) as email_attachments, values(attachment{}.sha256) as attachment_sha256, values(payload_size) as payload_size by destination{}.service num_message_attachments subject destination{}.address source.address phase severity
| `security_content_ctime(firstTime)`
| `security_content_ctime(lastTime)`
| `gsuite_email_suspicious_attachment_filter`
Macros
The SPL above uses the following Macros:
Note that gsuite_email_suspicious_attachment_filter is a empty macro by default. It allows the user to filter out any results (false positives) without editing the SPL.
Required field
- _time
- attachment{}.file_extension_type
- attachment{}.sha256
- destination{}.service
- num_message_attachments
- payload_size
- subject
- destination{}.address
- source.address
How To Implement
To successfully implement this search, you need to be ingesting logs related to gsuite having the file attachment metadata like file type, file extension, source email, destination email, num of attachment and etc.
Known False Positives
network admin and normal user may send this file attachment as part of their day to day work. having a good protocol in attaching this file type to an e-mail may reduce the risk of having a spear phishing attack.
Associated Analytic story
RBA
Risk Score | Impact | Confidence | Message |
---|---|---|---|
49.0 | 70 | 70 | suspicious email from $source.address$ to $destination{}.address$ |
Reference
Test Dataset
Replay any dataset to Splunk Enterprise by using our replay.py tool or the UI. Alternatively you can replay a dataset into a Splunk Attack Range
source | version: 1