• Sublime Core Feed
Medium Severity

Suspicious message with unscannable Vercel link

Description

This rule detects messages with unscannable links to Vercel infrastructure with suspicious indicators in the subject or display name from an unsolicited sender.

References

No references.

Sublime Security
Created Jun 10th, 2025 • Last updated Jul 16th, 2025
Source
type.inbound
and (
  // few links
  0 < length(body.links) < 20
  // fewer unique root domain links
  and length(distinct(body.links, .href_url.domain.root_domain)) < 10
  // sender domain matches no body domains
  and all(body.links,
          .href_url.domain.root_domain != sender.email.domain.root_domain
          // sender email address in body looks like this
          or .href_url.url == sender.email.domain.root_domain
  )
)

// negate bouncebacks and undeliverables
and not any(attachments,
            .content_type in (
              "message/global-delivery-status",
              "message/delivery-status"
            )
)

// suspicious subject or display name
and (
  regex.icontains(subject.subject,
                  "termination.*notice",
                  "38417",
                  ":completed",
                  "[il1]{2}mit.*ma[il1]{2} ?bo?x",
                  "[il][il][il]egai[ -]",
                  "[li][li][li]ega[li] attempt",
                  "[ng]-?[io]n .*block",
                  "[ng]-?[io]n .*cancel",
                  "[ng]-?[io]n .*deactiv",
                  "[ng]-?[io]n .*disabl",
                  "action.*required",
                  "abandon.*package",
                  "about.your.account",
                  "acc(ou)?n?t (is )?on ho[li]d",
                  "acc(ou)?n?t.*terminat",
                  "acc(oun)?t.*[il1]{2}mitation",
                  "access.*limitation",
                  "account (will be )?block",
                  "account.*de-?activat",
                  "account.*locked",
                  "account.*re-verification",
                  "account.*security",
                  "account.*suspension",
                  "account.has.been",
                  "account.has.expired",
                  "account.will.be.blocked",
                  "account v[il]o[li]at",
                  "activity.*acc(oun)?t",
                  "almost.full",
                  "app[li]e.[il]d",
                  "authenticate.*account",
                  "been.*suspend",
                  "clos.*of.*account.*processed",
                  "confirm.your.account",
                  "courier.*able",
                  "crediential.*notif",
                  "deactivation.*in.*progress",
                  "delivery.*attempt.*failed",
                  "document.received",
                  "documented.*shared.*with.*you",
                  "dropbox.*document",
                  "e-?ma[il1]+ .{010}suspen",
                  "e-?ma[il1]{1} user",
                  "e-?ma[il1]{2} acc",
                  "e-?ma[il1]{2}.*up.?grade",
                  "e.?ma[il1]{2}.*server",
                  "e.?ma[il1]{2}.*suspend",
                  "email.update",
                  "faxed you",
                  "fraud(ulent)?.*charge",
                  "from.helpdesk",
                  "fu[il1]{2}.*ma[il1]+[ -]?box",
                  "has.been.*suspended",
                  "has.been.limited",
                  "have.locked",
                  "he[li]p ?desk upgrade",
                  "heipdesk",
                  "i[il]iega[il]",
                  "ii[il]ega[il]",
                  "incoming e?mail",
                  "incoming.*fax",
                  "lock.*security",
                  "ma[il1]{1}[ -]?box.*quo",
                  "ma[il1]{2}[ -]?box.*fu[il1]",
                  "ma[il1]{2}box.*[il1]{2}mit",
                  "ma[il1]{2}box stor",
                  "mail on.?hold",
                  "mail.*box.*migration",
                  "mail.*de-?activat",
                  "mail.update.required",
                  "mails.*pending",
                  "messages.*pending",
                  "missed.*shipping.*notification",
                  "missed.shipment.notification",
                  "must.update.your.account",
                  "new [sl][io]g?[nig][ -]?in from",
                  "new voice ?-?mail",
                  "notifications.*pending",
                  "office.*3.*6.*5.*suspend",
                  "office365",
                  "on google docs with you",
                  "online doc",
                  "password.*compromised",
                  "periodic maintenance",
                  "potential(ly)? unauthorized",
                  "refund not approved",
                  "report",
                  "revised.*policy",
                  "scam",
                  "scanned.?invoice",
                  "secured?.update",
                  "security breach",
                  "securlty",
                  "signed.*delivery",
                  "statement is ready",
                  "status of your .{314}? ?delivery",
                  "susp[il1]+c[il1]+ous.*act[il1]+v[il1]+ty",
                  "suspicious.*sign.*[io]n",
                  "suspicious.activit",
                  "temporar(il)?y deactivate",
                  "temporar[il1]{2}y disab[li]ed",
                  "temporarily.*lock",
                  "un-?usua[li].activity",
                  "unable.*deliver",
                  "unauthorized.*activit",
                  "unauthorized.device",
                  "undelivered message",
                  "unread.*doc",
                  "unusual.activity",
                  "upgrade.*account",
                  "upgrade.notice",
                  "urgent message",
                  "urgent.verification",
                  "v[il1]o[li1]at[il1]on security",
                  "va[il1]{1}date.*ma[il1]{2}[ -]?box",
                  "verification ?-?require",
                  "verification( )?-?need",
                  "verify.your?.account",
                  "web ?-?ma[il1]{2}",
                  "web[ -]?ma[il1]{2}",
                  "will.be.suspended",
                  "your (customer )?account .as",
                  "your.office.365",
                  "your.online.access"
  )
  or any($suspicious_subjects, strings.icontains(subject.subject, .))
  or regex.icontains(sender.display_name,
                     "Admin",
                     "Administrator",
                     "Alert",
                     "Assistant",
                     "Billing",
                     "Benefits",
                     "Bonus",
                     "CEO",
                     "CFO",
                     "CIO",
                     "CTO",
                     "Chairman",
                     "Claim",
                     "Confirm",
                     "Critical",
                     "Customer Service",
                     "Deal",
                     "Discount",
                     "Director",
                     "Exclusive",
                     "Executive",
                     "Fax",
                     "Free",
                     "Gift",
                     "/bHR/b",
                     "Helpdesk",
                     "Human Resources",
                     "Immediate",
                     "Important",
                     "Info",
                     "Information",
                     "Invoice",
                     '\bIT\b',
                     "Legal",
                     "Lottery",
                     "Management",
                     "Manager",
                     "Member Services",
                     "Notification",
                     "Offer",
                     "Operations",
                     "Order",
                     "Partner",
                     "Payment",
                     "Payroll",
                     "President",
                     "Premium",
                     "Prize",
                     "Receipt",
                     "Refund",
                     "Registrar",
                     "Required",
                     "Reward",
                     "Sales",
                     "Secretary",
                     "Security",
                     "Service",
                     "Signature",
                     "SSA",
                     "Storage",
                     "Support",
                     "Sweepstakes",
                     "System",
                     "Tax",
                     "Tech Support",
                     "Update",
                     "Upgrade",
                     "Urgent",
                     "Validate",
                     "Verify",
                     "VIP",
                     "Webmaster",
                     "Winner",
  )
  or any(body.links,
         strings.ends_with(.href_url.url, ".exe")
         or .href_url.domain.root_domain in $social_landing_hosts
         or .href_url.domain.domain in $free_subdomain_hosts
         or .href_url.domain.root_domain in $free_subdomain_hosts
  )
)

// link can't be scanned due to Vercel block page
and any(body.links,
        strings.icontains(ml.link_analysis(., mode="aggressive").final_dom.display_text,
                          "Vercel Security Checkpoint"
        )
        or strings.icontains(ml.link_analysis(., mode="aggressive").final_dom.raw,
                             'https://vercel.link/security-checkpoint'
        )
)
and (
  not profile.by_sender_email().solicited
  or (
    profile.by_sender().any_messages_malicious_or_spam
    and not profile.by_sender().any_messages_benign
  )
)
// negate highly trusted sender domains unless they fail DMARC authentication
and (
  (
    sender.email.domain.root_domain in $high_trust_sender_root_domains
    and not headers.auth_summary.dmarc.pass
  )
  or sender.email.domain.root_domain not in $high_trust_sender_root_domains
)
and not profile.by_sender().any_messages_benign
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