High Severity
VIP Impersonation via Google Group relay with suspicious indicators
Description
Public Google Groups can be used to impersonate internal senders, while the reply to address is not under organizational control, leading to fraud, credential phishing, or other unwanted outcomes.
References
No references.
Sublime Security
Created Jan 19th, 2024 • Last updated May 3rd, 2024
Feed Source
Sublime Core Feed
Source
(type.inbound or type.internal)
and sender.email.domain.root_domain in $org_domains
// subject, sender or reply to contains a VIP
and (
any(headers.reply_to,
any($org_vips, strings.contains(.display_name, ..display_name))
)
or any($org_vips, strings.contains(subject.subject, .display_name))
or any($org_vips, strings.contains(sender.display_name, .display_name))
)
and any(headers.hops,
any(.fields,
regex.icontains(.name,
"X-Authenticated-Sender|X-Sender|X-Original-Sender"
)
)
)
// reply to return path mismatch and not org domain
and any(headers.reply_to,
.email.domain.root_domain != headers.return_path.domain.root_domain
and .email.domain.root_domain not in $org_domains
)
// googlegroups found in hops
and any(headers.hops,
.index == 0 and any(.fields, strings.icontains(.value, "googlegroups"))
)
// financial nlu entity in current thread
and 3 of (
any(ml.nlu_classifier(body.current_thread.text).entities,
.name == "financial"
),
// invoice entity in display_text
any(ml.nlu_classifier(body.current_thread.text).tags, .name == "invoice"),
// fake thread
(
regex.imatch(subject.subject, "(re|fw(d)?):.*")
and (
(length(headers.references) == 0 and headers.in_reply_to is null)
or not any(headers.hops,
any(.fields, strings.ilike(.name, "In-Reply-To"))
)
)
),
// reply-to is freemail
any(headers.reply_to, .email.domain.domain in $free_email_providers),
// reply-to is not in $recipient_emails
any(headers.reply_to, .email.email not in $recipient_emails),
// dmarc authentication is freemail provider
headers.auth_summary.dmarc.details.from.root_domain in $free_email_providers
)
Playground
Test against your own EMLs or sample data.