sublimemediumRule

Link: Single character path with credential theft body and self sender behavior or invalid recipient

Message where the sender and recipient are the same or the recipient domain is invalid, contains a link with a single character path and no query parameters or fragments, and includes credential theft language.

MITRE ATT&CK

T1566 T1566.001 T1566.002 T1598 T1036 T1027

defense-evasioninitial-access

Detection Query

type.inbound
// self sender or invaild recipent domain
and length(recipients.to) == 1
and (
  sender.email.email == recipients.to[0].email.email
  or recipients.to[0].email.domain.valid == false
)
// path contains 1 character
and any(body.current_thread.links,
        regex.imatch(.href_url.path, '\/[A-Za-z0-9]')
        and .href_url.query_params is null
        and .href_url.fragment is null
        and .display_url.url is null
)
and any(ml.nlu_classifier(body.current_thread.text).intents,
        .name == "cred_theft" and .confidence != "low"
)

Data Sources

Email MessagesEmail HeadersEmail Attachments

Platforms

Raw Content

name: "Link: Single character path with credential theft body and self sender behavior or invalid recipient"
description: "Message where the sender and recipient are the same or the recipient domain is invalid, contains a link with a single character path and no query parameters or fragments, and includes credential theft language."
type: "rule"
severity: "medium"
source: |
  type.inbound
  // self sender or invaild recipent domain
  and length(recipients.to) == 1
  and (
    sender.email.email == recipients.to[0].email.email
    or recipients.to[0].email.domain.valid == false
  )
  // path contains 1 character
  and any(body.current_thread.links,
          regex.imatch(.href_url.path, '\/[A-Za-z0-9]')
          and .href_url.query_params is null
          and .href_url.fragment is null
          and .display_url.url is null
  )
  and any(ml.nlu_classifier(body.current_thread.text).intents,
          .name == "cred_theft" and .confidence != "low"
  )
attack_types:
  - "Credential Phishing"
tactics_and_techniques:
  - "Evasion"
  - "Social engineering"
detection_methods:
  - "Natural Language Understanding"
  - "URL analysis"
  - "Sender analysis"
  - "Header analysis"
id: "c97982e6-eaa2-53e3-ba8f-0dc4db55b936"