Brand impersonation: AuthentiSign

calendar Jan 21, 2026  ·
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Detects messages impersonating AuthentiSign through display name, domain, subject, or body content that either originate from non-AuthentiSign or spoofed domains.

Sublime rule (View on GitHub)

 1name: "Brand impersonation: AuthentiSign"
 2description: "Detects messages impersonating AuthentiSign through display name, domain, subject, or body content that either originate from non-AuthentiSign or spoofed domains."
 3type: "rule"
 4severity: "medium"
 5source: |
 6  type.inbound
 7  and strings.icontains(body.current_thread.text, "authentisign")
 8  and (
 9    regex.icontains(body.current_thread.text, 'signing (?:name|party)')
10    or strings.ilike(sender.display_name, '*authentisign*')
11    or strings.ilevenshtein(sender.display_name, 'authentisign') <= 1
12    or strings.ilike(sender.email.domain.domain, '*authentisign*')
13  )
14  and (
15    sender.email.domain.root_domain != "authentisign.com"
16    or (
17      sender.email.domain.root_domain == "authentisign.com"
18      and not (headers.auth_summary.spf.pass or headers.auth_summary.dmarc.pass)
19    )
20  )  
21
22attack_types:
23  - "Credential Phishing"
24  - "BEC/Fraud"
25tactics_and_techniques:
26  - "Impersonation: Brand"
27  - "Lookalike domain"
28  - "Social engineering"
29detection_methods:
30  - "Content analysis"
31  - "Header analysis"
32  - "Sender analysis"
33id: "445a8c8b-cd38-5161-bf56-2eab83419e24"
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