Email attachment with multiple extensions

Synopsis

Field	Value
Activation Period	14 Days
Training Period	30 Days
Test Period	N/A (single event)
Deduplication Period	1 Hour 30 Minutes
Required Data	Microsoft 365 Emails
Detection Modules	Email
ATT&CK Tactic	Execution (TA0002), Stealth (TA0005)
ATT&CK Technique	User Execution: Malicious File (T1204.002), Masquerading: Double File Extension (T1036.007)
Severity	Informational

Description

The email includes an attachment(s) with two extensions. The first one being an executable extension.

• This may indicate an attempt at masquerading the true file type through the misuse of multiple extensions in the attachment name.

Attacker's Goals

Trick users into interacting with malicious attachments that seem legitimate.

• Deploy malicious attachments through emails to compromise systems or gain unauthorized access.

Investigative actions

• Check the file types and investigate the legitimacy of files intended to be sent via email.
• Scrutinize the attachments for any suspicious indications.
• Confirm whether the attachments were successfully delivered to the recipient's mailbox.
• If the attachments were delivered successfully, verify whether the recipient downloaded them.
• Check the email address for any unusual spellings or missing letters.
• Verify the sender's address to confirm its legitimacy.
• Check for previous emails from the sender's address.

Variations

Email executable attachment with multiple extensions

Synopsis

Field	Value
ATT&CK Tactic	Execution (TA0002), Stealth (TA0005)
ATT&CK Technique	User Execution: Malicious File (T1204.002), Masquerading: Double File Extension (T1036.007)
Severity	Low

Description

This email includes attachment(s) with multiple extensions, where the last extension is an executable extension.

• This could be a potential attempt to trick the user into executing such file(s).

Attacker's Goals

Trick users into interacting with malicious attachments that seem legitimate.

• Deploy malicious attachments through emails to compromise systems or gain unauthorized access.

Investigative actions

• Check the file types and investigate the legitimacy of files intended to be sent via email.
• Scrutinize the attachments for any suspicious indications.
• Confirm whether the attachments were successfully delivered to the recipient's mailbox.
• If the attachments were delivered successfully, verify whether the recipient downloaded them.
• Check the email address for any unusual spellings or missing letters.
• Verify the sender's address to confirm its legitimacy.
• Check for previous emails from the sender's address.

Email executable attachment with multiple executable extensions

Synopsis

Field	Value
ATT&CK Tactic	Execution (TA0002), Stealth (TA0005)
ATT&CK Technique	User Execution: Malicious File (T1204.002), Masquerading: Double File Extension (T1036.007)
Severity	Low

Description

This email includes attachment(s) with multiple executable extensions that are different.

• This could be a potential attempt to trick the user into executing such file(s).

Attacker's Goals

Trick users into interacting with malicious attachments that seem legitimate.

• Deploy malicious attachments through emails to compromise systems or gain unauthorized access.

Investigative actions

• Check the file types and investigate the legitimacy of files intended to be sent via email.
• Scrutinize the attachments for any suspicious indications.
• Confirm whether the attachments were successfully delivered to the recipient's mailbox.
• If the attachments were delivered successfully, verify whether the recipient downloaded them.
• Check the email address for any unusual spellings or missing letters.
• Verify the sender's address to confirm its legitimacy.
• Check for previous emails from the sender's address.