Brand impersonation: Sharepoint fake file share

 1name: "Brand impersonation: Sharepoint fake file share"
 2description: |
 3    This rule detects messages impersonating a Sharepoint file sharing email where no links point to known Microsoft domains.
 4type: "rule"
 5severity: "medium"
 6source: |
 7  type.inbound
 8  
 9  // Sharepoint body content looks like this
10  and strings.contains(body.current_thread.text, "shared a file with you")
11  and strings.icontains(subject.subject, "shared")
12  and any(ml.logo_detect(beta.message_screenshot()).brands, .name == "Microsoft")
13  
14  // fake Sharepoint shares are easy to identify if there are any links
15  // that don't point to microsoft[.]com or *.sharepoint[.]com
16  and not all(body.links,
17              .href_url.domain.root_domain in ("microsoft.com", "sharepoint.com")
18  )
19  and sender.email.domain.root_domain not in $org_domains
20  and sender.email.domain.root_domain not in (
21    "bing.com",
22    "microsoft.com",
23    "microsoftonline.com",
24    "microsoftsupport.com",
25    "microsoft365.com",
26    "office.com",
27    "onedrive.com",
28    "sharepointonline.com",
29    "yammer.com",
30    //ignore microsoft privacy statement links
31    "aka.ms"
32  )
33  
34  // negate highly trusted sender domains unless they fail DMARC authentication
35  and (
36    (
37      sender.email.domain.root_domain in $high_trust_sender_root_domains
38      and (
39        any(distinct(headers.hops, .authentication_results.dmarc is not null),
40            strings.ilike(.authentication_results.dmarc, "*fail")
41        )
42      )
43    )
44    or sender.email.domain.root_domain not in $high_trust_sender_root_domains
45  )
46  and (
47    (
48      not profile.by_sender().solicited
49    )
50    or (
51      profile.by_sender().any_messages_malicious_or_spam
52      and not profile.by_sender().any_false_positives
53    )
54  )
55  and not profile.by_sender().any_false_positives  
56
57attack_types:
58  - "Credential Phishing"
59  - "Malware/Ransomware"
60detection_methods:
61  - "Content analysis"
62  - "Header analysis"
63  - "URL analysis"
64  - "Computer Vision"
65tactics_and_techniques:
66  - "Impersonation: Brand"
67  - "Social engineering"
68id: "ff8b296b-aa0d-5df0-b4d2-0e599b688f6a"