sublimemediumRule

Link: Hex-encoded recipient email in URL fragment

Detects messages where a link in the body contains the recipient's email address hex-encoded in the URL fragment, a technique used to auto-populate or validate the target on a credential harvesting page. This pattern commonly appears in fake password expiration or account notice lures that direct victims to spoofed login pages pre-filled with their own address to increase credibility.

MITRE ATT&CK

T1566 T1566.001 T1566.002 T1598 T1027 T1573 T1036

defense-evasioninitial-access

Detection Query

type.inbound
and any(body.links,
        strings.decode_hex(.href_url.fragment) == recipients.to[0].email.email
)

Data Sources

Email MessagesEmail HeadersEmail Attachments

Platforms

Tags

Attack surface reduction

Raw Content

name: "Link: Hex-encoded recipient email in URL fragment"
description: "Detects messages where a link in the body contains the recipient's email address hex-encoded in the URL fragment, a technique used to auto-populate or validate the target on a credential harvesting page. This pattern commonly appears in fake password expiration or account notice lures that direct victims to spoofed login pages pre-filled with their own address to increase credibility."
type: "rule"
severity: "medium"
source: |
  type.inbound
  and any(body.links,
          strings.decode_hex(.href_url.fragment) == recipients.to[0].email.email
  )
tags:
  - "Attack surface reduction"
attack_types:
  - "Credential Phishing"
tactics_and_techniques:
  - "Encryption"
  - "Evasion"
  - "Social engineering"
detection_methods:
  - "URL analysis"
  - "Content analysis"
id: "046ed6f2-4825-5b41-9410-630113920ba3"