Suspicious SPF Result

Synopsis

Field	Value
Activation Period	14 Days
Training Period	30 Days
Test Period	N/A (single event)
Deduplication Period	1 Day
Required Data	Microsoft 365 Emails
Detection Modules	Email
Detector Tags	Spoofing
ATT&CK Tactic	Stealth (TA0005)
ATT&CK Technique	Social Engineering: Impersonation (T1684.001)
Severity	Informational

Description

The email has a suspicious SPF result of fail, soft fail, or policy, which may indicate a potential domain misconfiguration or spoofing.

Attacker's Goals

Impersonate internal users or familiar individuals.

• Trick users into clicking on malicious links or attachments.

Investigative actions

• Check the email address for any unusual spellings.
• Check the email address for any missing letters.
• Verify the sender's domain to confirm its legitimacy.
• Examine the sender's IP address and reputation.
• Verify the domain's connection to the IP address and investigate the reason SPF didn't pass.
• Verify whether the sender's IP address has appeared in different log sources before.
• Verify if the sender's IP address is identifiable.
• If the message contains attachments or links, scrutinize them for any suspicious indications.
• Monitor further actions taken, such as file downloads or access to potentially malicious links.

Variations

Internal domain SPF deviation

Synopsis

Field	Value
ATT&CK Tactic	Stealth (TA0005)
ATT&CK Technique	Social Engineering: Impersonation (T1684.001)
Severity	Informational

Description

• An email was sent from an internal root domain that has historically passed SPF checks, but returned a suspicious SPF result of fail, soft fail, or policy for the first time in the past 30 days.
• This deviation may indicate an attempt to spoof or impersonate a trusted internal sender, a tactic commonly associated with BEC and internal phishing.
• Such a sudden SPF outcome from a typically trusted domain warrants further investigation.

Attacker's Goals

Impersonate internal users or familiar individuals.

• Trick users into clicking on malicious links or attachments.

Investigative actions

• Check the email address for any unusual spellings.
• Check the email address for any missing letters.
• Verify the sender's domain to confirm its legitimacy.
• Examine the sender's IP address and reputation.
• Verify the domain's connection to the IP address and investigate the reason SPF didn't pass.
• Verify whether the sender's IP address has appeared in different log sources before.
• Verify if the sender's IP address is identifiable.
• If the message contains attachments or links, scrutinize them for any suspicious indications.
• Monitor further actions taken, such as file downloads or access to potentially malicious links.

Known domain SPF deviation

Synopsis

Field	Value
ATT&CK Tactic	Stealth (TA0005)
ATT&CK Technique	Social Engineering: Impersonation (T1684.001)
Severity	Informational

Description

• An email was sent from a domain that has historically passed SPF checks, but returned a suspicious SPF result of fail, soft fail, or policy for the first time in the past 30 days.
• This deviation may indicate an attempt to spoof or impersonate a legitimate external sender.
• Such a sudden SPF outcome from a previously trusted external domain warrants further investigation.

Attacker's Goals

Impersonate internal users or familiar individuals.

• Trick users into clicking on malicious links or attachments.

Investigative actions

• Check the email address for any unusual spellings.
• Check the email address for any missing letters.
• Verify the sender's domain to confirm its legitimacy.
• Examine the sender's IP address and reputation.
• Verify the domain's connection to the IP address and investigate the reason SPF didn't pass.
• Verify whether the sender's IP address has appeared in different log sources before.
• Verify if the sender's IP address is identifiable.
• If the message contains attachments or links, scrutinize them for any suspicious indications.
• Monitor further actions taken, such as file downloads or access to potentially malicious links.