Detection rules › Sublime MQL

Open redirect: documentmailbox.com

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

Message contains use of the documentmailbox.com open redirect. This has been exploited in the wild.

Threat classification

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

CategoryValues
Attack typesCredential Phishing, Malware/Ransomware
Tactics and techniquesOpen redirect

Event coverage

Rule body MQL

type.inbound
and any(body.links,
        .href_url.domain.root_domain == "documentmailbox.com"
        and strings.icontains(.href_url.path, 'RedirectTarget.aspx')
        and strings.icontains(.href_url.query_params, 'TargetUrl=')
)
and length(filter(body.links,
                  .href_url.domain.root_domain == "documentmailbox.com"
                  and strings.icontains(.href_url.path, 'RedirectTarget.aspx')
                  and strings.icontains(.href_url.query_params, 'TargetUrl=')
           )
) == 1

// 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
)

Detection logic

Scope: inbound message.

Message contains use of the documentmailbox.com open redirect. This has been exploited in the wild.

  1. inbound message
  2. any of body.links where all hold:
    • .href_url.domain.root_domain is 'documentmailbox.com'
    • .href_url.path contains 'RedirectTarget.aspx'
    • .href_url.query_params contains 'TargetUrl='
  3. length(filter(body.links, .href_url.domain.root_domain == 'documentmailbox.com' and strings.icontains(.href_url.path, 'RedirectTarget.aspx') and strings.icontains(.href_url.query_params, 'TargetUrl='))) is 1
  4. 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.links, body.links[].href_url.domain.root_domain, body.links[].href_url.path, body.links[].href_url.query_params, headers.auth_summary.dmarc.pass, sender.email.domain.root_domain, type.inbound. Sensors: strings.icontains. Reference lists: $high_trust_sender_root_domains.

Indicators matched (3)

FieldMatchValue
body.links[].href_url.domain.root_domainequalsdocumentmailbox.com
strings.icontainssubstringRedirectTarget.aspx
strings.icontainssubstringTargetUrl=