sublimecriticalRule

Link: Self-sent message with quarterly document review request

Detects messages sent from a user to themselves containing a link with quarterly indicators (q1_, q2_, q3_, q4_) and specific document review language requesting urgent feedback.

MITRE ATT&CK

T1566.002 T1534 T1656 T1566 T1566.001 T1598 T1036 T1027

initial-accessdefense-evasion

Detection Query

type.inbound
// self sender
and length(recipients.to) == 1
and length(recipients.cc) == 0
and length(recipients.bcc) == 0
and (
  sender.email.email == recipients.to[0].email.email
  or recipients.to[0].email.domain.valid == false
)
// first link is not related to the sender via sld (to account for orgs that have multiple tlds)
and body.current_thread.links[0].href_url.domain.sld != sender.email.domain.sld
and regex.icontains(body.current_thread.links[0].display_text, 'q[1-4]_20')

Data Sources

Email MessagesEmail HeadersEmail Attachments

Platforms

Raw Content

name: "Link: Self-sent message with quarterly document review request"
description: "Detects messages sent from a user to themselves containing a link with quarterly indicators (q1_, q2_, q3_, q4_) and specific document review language requesting urgent feedback."
type: "rule"
severity: "critical"
source: |
  type.inbound
  // self sender
  and length(recipients.to) == 1
  and length(recipients.cc) == 0
  and length(recipients.bcc) == 0
  and (
    sender.email.email == recipients.to[0].email.email
    or recipients.to[0].email.domain.valid == false
  )
  // first link is not related to the sender via sld (to account for orgs that have multiple tlds)
  and body.current_thread.links[0].href_url.domain.sld != sender.email.domain.sld
  and regex.icontains(body.current_thread.links[0].display_text, 'q[1-4]_20')
attack_types:
  - "BEC/Fraud"
  - "Credential Phishing"
tactics_and_techniques:
  - "Social engineering"
  - "Evasion"
detection_methods:
  - "Content analysis"
  - "Header analysis"
  - "Sender analysis"
  - "URL analysis"
id: "3c42cec6-c887-5f68-8083-b1397f274f4b"