VIP / Executive impersonation (untrusted)

 1name: "VIP / Executive impersonation (untrusted)"
 2description: |
 3  Sender display name matches the display name of a user in the $org_vips list, and the sender has never been seen before.
 4
 5  The $org_vips list must first be manually connected to a VIP group of your upstream provider (Google Workspace and Microsoft 365 only) in order for this rule to work.
 6  Once connected, the list will be automatically synced and kept up-to-date. For more information, see the $org_vips documentation: https://docs.sublimesecurity.com/docs/configure-org_vips-list
 7
 8  This rule is recommended to be used on a relatively small list of VIPs, and is meant to reduce attack surface by detecting *any* message that matches the protected list of display names from a first-time or unsolicited sender.
 9
10  Additional rule logic can be added to look for suspicious subjects, suspicious links, etc.  
11type: "rule"
12severity: "high"
13source: |
14  type.inbound
15  and any($org_vips, .display_name =~ sender.display_name)
16  and (
17    // ignore personal <> work emails
18    // where the sender and mailbox's display name are the same
19    length(recipients.to) > 0
20    or length(recipients.cc) > 0
21    or sender.display_name != mailbox.display_name
22  )
23  // bounce-back negations
24  and not strings.like(sender.email.local_part, "*postmaster*", "*mailer-daemon*", "*administrator*")
25  and not any(attachments,
26              .content_type in (
27                "message/rfc822",
28                "message/delivery-status",
29                "text/calendar"
30              )
31  )
32  and (
33    (
34      profile.by_sender().prevalence in ("new", "outlier")
35      and not profile.by_sender().solicited
36    )
37    or (
38      profile.by_sender().any_messages_malicious_or_spam
39      and not profile.by_sender().any_false_positives
40    )
41  )
42  and (
43    (
44      sender.email.domain.root_domain in $org_domains
45      and not headers.auth_summary.dmarc.pass
46    )
47    or sender.email.domain.root_domain not in $org_domains
48  )
49  and not profile.by_sender().any_false_positives  
50
51tags:
52  - "Attack surface reduction"
53attack_types:
54  - "BEC/Fraud"
55tactics_and_techniques:
56  - "Impersonation: VIP"
57detection_methods:
58  - "Header analysis"
59  - "Sender analysis"
60id: "e42c84b7-9d50-5870-9a5d-311670a14bc1"