Mass campaign: recipient address in subject, body, and link (untrusted sender)

This detects a pattern commonly observed in mass phishing campaigns.

The local_part or the full email address of the recipient is used in the subject, body, and link query parameter to "personalize" the attack.

Sublime rule (View on GitHub)

 1name: "Mass campaign: recipient address in subject, body, and link (untrusted sender)"
 2description: |
 3  This detects a pattern commonly observed in mass phishing campaigns.
 4
 5  The local_part or the full email address of the recipient is used in the subject,
 6  body, and link query parameter to "personalize" the attack.  
 7references:
 8  - "https://playground.sublimesecurity.com?id=d9143109-8886-4639-b634-d0a671848eb6"
 9type: "rule"
10severity: "medium"
11source: |
12  type.inbound
13  and length(recipients.to) + length(recipients.bcc) + length(recipients.cc) == 1
14
15  // exclude To: Undisclosed recipients:;
16  // since we won't have a valid recipient email
17  and any(recipients.to, .email.domain.valid == true)
18  and (
19    profile.by_sender().prevalence in ("new", "outlier")
20    or (
21      profile.by_sender().any_messages_malicious_or_spam
22      and not profile.by_sender().any_false_positives
23    )
24  )
25  and (
26    any(recipients.to,
27        (
28          strings.icontains(subject.subject, .email.email)
29          or strings.icontains(subject.subject, .email.local_part)
30        )
31        and (.email.domain.valid or strings.icontains(.display_name, "undisclosed"))
32    )
33  )
34  and any([body.html.inner_text, body.plain.raw],
35          any(recipients.to, strings.icontains(.., .email.email))
36  )
37  and any(body.links, any(recipients.to, strings.icontains(..href_url.query_params, .email.email)))
38  and any(ml.nlu_classifier(coalesce(body.html.display_text, body.plain.raw)).intents,
39          .name in ("cred_theft") and .confidence == "high"
40  )
41  and any(ml.nlu_classifier(body.current_thread.text).intents,
42          .name in ("cred_theft") and .confidence == "high"
43  )
44  
45  // negate highly trusted sender domains unless they fail DMARC authentication
46  and (
47    (
48      sender.email.domain.root_domain in $high_trust_sender_root_domains
49      and (
50        any(distinct(headers.hops, .authentication_results.dmarc is not null),
51            strings.ilike(.authentication_results.dmarc, "*fail")
52        )
53      )
54    )
55    or sender.email.domain.root_domain not in $high_trust_sender_root_domains
56  )  
57attack_types:
58  - "Credential Phishing"
59tactics_and_techniques:
60  - "Social engineering"
61detection_methods:
62  - "Header analysis"
63  - "Natural Language Understanding"
64  - "Sender analysis"
65id: "599dabf5-6287-5adf-8a8f-70649ccf0f92"
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