Detection rules › Sublime MQL

Brand impersonation: United Healthcare

Severity
medium
Type
rule
Source
github.com/sublime-security/sublime-rules

Detects messages impersonating United Healthcare (UHC) by analyzing display names that contain variations of 'United Healthcare' or 'UHC', including those with character substitutions. The rule excludes legitimate messages from verified UHC domains that pass DMARC authentication and handles high-trust sender domains appropriately.

Threat classification

Sublime's own taxonomy (not MITRE ATT&CK).

CategoryValues
Attack typesCredential Phishing
Tactics and techniquesImpersonation: Brand, Social engineering

Event coverage

Rule body MQL

type.inbound
and (
  // display name contains UHC
  (
    strings.ilike(strings.replace_confusables(sender.display_name),
                  '*united healthcare*'
    )
    or strings.ilike(strings.replace_confusables(sender.display_name), 'UHC*')
    or regex.icontains(sender.display_name, 'united ?health ?care')
  )
  // levenshtein distance similar to UHC
  or strings.ilevenshtein(strings.replace_confusables(sender.display_name),
                          'united healthcare'
  ) <= 1
  or (
    regex.icontains(body.current_thread.text, 'united ?health ?care')
    and (
      regex.icontains(body.current_thread.text, 'quick .{0,10}survey')
      // Free benefits/items lure commonly used in UHC impersonation
      or regex.icontains(body.current_thread.text,
                         'dental (benefits?|coverage).{0,50}(free|eligible|no.{0,10}cost)'
      )
      or regex.icontains(body.current_thread.text,
                         'free.{0,30}(toothbrush|dental|benefit)'
      )
    )
  )
  // Brand name in sender local part from non-UHC domain
  or (
    strings.icontains(sender.email.local_part, "unitedhealthcare")
    and sender.email.domain.root_domain not in (
      "uhc.com",
      "unitedhealthcare.com",
      "uhcmedicaresolutions.com",
      "unitedhealthcareupdate.com",
      "yourhealth-wellnessteam.com",
      "uhc-customer.com",
      "leavesource.com"
    )
  )
)
// and the sender is not in org_domains or from UHC domains and passes auth
and not (
  sender.email.domain.root_domain in $org_domains
  or (
    (
      sender.email.domain.root_domain in (
        "uhc.com",
        "unitedhealthcare.com",
        "uhcmedicaresolutions.com",
        "unitedhealthcareupdate.com",
        "yourhealth-wellnessteam.com",
        "uhc-customer.com",
        "leavesource.com"
      )
      or sender.display_name in (
        "UHCOM Faculty Affairs",
        "UHC Construction Services"
      )
    )
    and headers.auth_summary.dmarc.pass
  )
)
// negate UHC job related posting
and not any(ml.nlu_classifier(body.current_thread.text).topics,
            .name == "Professional and Career Development"
            and .confidence == "high"
)
// and the sender is not from high trust sender root domains
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
)

Detection logic

Scope: inbound message.

Detects messages impersonating United Healthcare (UHC) by analyzing display names that contain variations of 'United Healthcare' or 'UHC', including those with character substitutions. The rule excludes legitimate messages from verified UHC domains that pass DMARC authentication and handles high-trust sender domains appropriately.

  1. inbound message
  2. any of:
    • any of:
      • strings.replace_confusables(sender.display_name) matches '*united healthcare*'
      • strings.replace_confusables(sender.display_name) matches 'UHC*'
      • sender.display_name matches 'united ?health ?care'
    • strings.replace_confusables(sender.display_name) is similar to 'united healthcare'
    • all of:
      • body.current_thread.text matches 'united ?health ?care'
      • any of:
        • body.current_thread.text matches 'quick .{0,10}survey'
        • body.current_thread.text matches 'dental (benefits?|coverage).{0,50}(free|eligible|no.{0,10}cost)'
        • body.current_thread.text matches 'free.{0,30}(toothbrush|dental|benefit)'
    • all of:
      • sender.email.local_part contains 'unitedhealthcare'
      • sender.email.domain.root_domain not in ('uhc.com', 'unitedhealthcare.com', 'uhcmedicaresolutions.com', 'unitedhealthcareupdate.com', 'yourhealth-wellnessteam.com', 'uhc-customer.com', 'leavesource.com')
  3. none of:
    • sender.email.domain.root_domain in $org_domains
    • all of:
      • any of:
        • sender.email.domain.root_domain in ('uhc.com', 'unitedhealthcare.com', 'uhcmedicaresolutions.com', 'unitedhealthcareupdate.com', 'yourhealth-wellnessteam.com', 'uhc-customer.com', 'leavesource.com')
        • sender.display_name in ('UHCOM Faculty Affairs', 'UHC Construction Services')
      • headers.auth_summary.dmarc.pass
  4. not:
    • any of ml.nlu_classifier(body.current_thread.text).topics where all hold:
      • .name is 'Professional and Career Development'
      • .confidence is 'high'
  5. any of:
    • all of:
      • sender.email.domain.root_domain in $high_trust_sender_root_domains
      • not:
        • headers.auth_summary.dmarc.pass
    • sender.email.domain.root_domain not in $high_trust_sender_root_domains

Inspects: body.current_thread.text, headers.auth_summary.dmarc.pass, sender.display_name, sender.email.domain.root_domain, sender.email.local_part, type.inbound. Sensors: ml.nlu_classifier, regex.icontains, strings.icontains, strings.ilevenshtein, strings.ilike, strings.replace_confusables. Reference lists: $high_trust_sender_root_domains, $org_domains.

Indicators matched (19)

FieldMatchValue
strings.ilikesubstring*united healthcare*
strings.ilikesubstringUHC*
regex.icontainsregexunited ?health ?care
strings.ilevenshteinfuzzyunited healthcare
regex.icontainsregexquick .{0,10}survey
regex.icontainsregexdental (benefits?|coverage).{0,50}(free|eligible|no.{0,10}cost)
regex.icontainsregexfree.{0,30}(toothbrush|dental|benefit)
strings.icontainssubstringunitedhealthcare
sender.email.domain.root_domainmemberuhc.com
sender.email.domain.root_domainmemberunitedhealthcare.com
sender.email.domain.root_domainmemberuhcmedicaresolutions.com
sender.email.domain.root_domainmemberunitedhealthcareupdate.com
7 more
sender.email.domain.root_domainmemberyourhealth-wellnessteam.com
sender.email.domain.root_domainmemberuhc-customer.com
sender.email.domain.root_domainmemberleavesource.com
sender.display_namememberUHCOM Faculty Affairs
sender.display_namememberUHC Construction Services
ml.nlu_classifier(body.current_thread.text).topics[].nameequalsProfessional and Career Development
ml.nlu_classifier(body.current_thread.text).topics[].confidenceequalshigh