ID | Technique | Tactic |
---|---|---|
T1566.001 | Spearphishing Attachment | Initial Access |
T1566 | Phishing | Initial Access |
Detection: GSuite Email Suspicious Attachment
Description
The following analytic detects suspicious attachment file extensions in GSuite emails, potentially indicating a spear-phishing attack. It leverages GSuite Gmail logs to identify emails with attachments having file extensions commonly associated with malware, such as .exe, .bat, and .js. This activity is significant as these file types are often used to deliver malicious payloads, posing a risk of compromising targeted machines. If confirmed malicious, this could lead to unauthorized code execution, data breaches, or further network infiltration.
Search
1`gsuite_gmail` "attachment{}.file_extension_type" IN ("pl", "py", "rb", "sh", "bat", "exe", "dll", "cpl", "com", "js", "vbs", "ps1", "reg","swf", "cmd", "go")
2| eval phase="plan"
3| eval severity="medium"
4| 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
5| `security_content_ctime(firstTime)`
6| `security_content_ctime(lastTime)`
7| `gsuite_email_suspicious_attachment_filter`
Data Source
Name | Platform | Sourcetype | Source |
---|---|---|---|
G Suite Gmail | N/A | 'gsuite:gmail:bigquery' |
'http:gsuite' |
Macros Used
Name | Value |
---|---|
gsuite_gmail | sourcetype=gsuite:gmail:bigquery |
gsuite_email_suspicious_attachment_filter | search * |
gsuite_email_suspicious_attachment_filter
is an empty macro by default. It allows the user to filter out any results (false positives) without editing the SPL.
Annotations
Default Configuration
This detection is configured by default in Splunk Enterprise Security to run with the following settings:
Setting | Value |
---|---|
Disabled | true |
Cron Schedule | 0 * * * * |
Earliest Time | -70m@m |
Latest Time | -10m@m |
Schedule Window | auto |
Creates Risk Event | True |
Implementation
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
Risk Based Analytics (RBA)
Risk Message | Risk Score | Impact | Confidence |
---|---|---|---|
Suspicious email from $source.address$ to $destination{}.address$ | 49 | 70 | 70 |
References
Detection Testing
Test Type | Status | Dataset | Source | Sourcetype |
---|---|---|---|---|
Validation | ✅ Passing | N/A | N/A | N/A |
Unit | ✅ Passing | Dataset | http:gsuite |
gsuite:gmail:bigquery |
Integration | ✅ Passing | Dataset | http:gsuite |
gsuite:gmail:bigquery |
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: GitHub | Version: 3