Link: Self-sent message with quarterly document review request

 1name: "Link: Self-sent message with quarterly document review request"
 2description: "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."
 3type: "rule"
 4severity: "critical"
 5source: |
 6  type.inbound
 7  // self sender
 8  and length(recipients.to) == 1
 9  and length(recipients.cc) == 0
10  and length(recipients.bcc) == 0
11  and (
12    sender.email.email == recipients.to[0].email.email
13    or recipients.to[0].email.domain.valid == false
14  )
15  // first link is not related to the sender via sld (to account for orgs that have multiple tlds)
16  and body.current_thread.links[0].href_url.domain.sld != sender.email.domain.sld
17  and regex.icontains(body.current_thread.links[0].display_text, 'q[1-4][ _]20')
18  and (
19    strings.contains(body.current_thread.links[0].display_text, '#')
20    or strings.contains(subject.base, '#')
21    or regex.contains(subject.base, '^[^a-z]*$')
22  )  
23attack_types:
24  - "BEC/Fraud"
25  - "Credential Phishing"
26tactics_and_techniques:
27  - "Social engineering"
28  - "Evasion"
29detection_methods:
30  - "Content analysis"
31  - "Header analysis"
32  - "Sender analysis"
33  - "URL analysis"
34id: "3c42cec6-c887-5f68-8083-b1397f274f4b"