Suspicious newly registered reply-to domain with engaging financial or urgent language

 1name: "Suspicious newly registered reply-to domain with engaging financial or urgent language"
 2description: |
 3  Detects messages from a mismatched newly registered Reply-to domain that contain a financial or urgent request, or a request and 
 4  an NLU tag with medium to high confidence, from an untrusted sender. This technique is typically observed in Vendor impersonation.  
 5type: "rule"
 6severity: "medium"
 7source: |
 8  type.inbound
 9  and length(body.current_thread.text) < 5000
10  and any(headers.reply_to,
11          // mismatched reply-to and sender domain
12          .email.domain.root_domain != sender.email.domain.root_domain
13          // newly registered reply-to domain
14          and network.whois(.email.domain).days_old <= 30
15  )
16  // request is being made
17  and any(ml.nlu_classifier(body.current_thread.text).entities, .name == "request")
18  // there's financial/urgency OR a tag of medium/high confidence
19  and (
20    any(ml.nlu_classifier(body.current_thread.text).entities, .name in ("financial", "urgency"))
21    or any(ml.nlu_classifier(body.current_thread.text).tags,
22           .name is not null and .confidence in ("medium", "high")
23    )
24  )
25  and (
26    not profile.by_sender().solicited
27    or (
28      profile.by_sender().any_messages_malicious_or_spam
29      and not profile.by_sender().any_false_positives
30    )
31  )
32  and not profile.by_sender().any_false_positives
33    
34attack_types:
35  - "BEC/Fraud"
36tactics_and_techniques:
37  - "Social engineering"
38detection_methods:
39  - "Content analysis"
40  - "Header analysis"
41  - "Natural Language Understanding"
42  - "Sender analysis"
43  - "URL analysis"
44  - "Whois"
45id: "db4d9bb3-0eca-5525-9a99-7c1c773b580f"