Detection rules › Sublime MQL
Headers: Invalid recipient domain with mismatched reply-to from new sender
Message sent to an invalid recipient domain with a reply-to address that differs from the sender address, originating from a new sender.
Threat classification
Sublime's own taxonomy (not MITRE ATT&CK).
| Category | Values |
|---|---|
| Attack types | BEC/Fraud, Credential Phishing, Spam |
| Tactics and techniques | Evasion, Social engineering |
Event coverage
Rule body MQL
type.inbound
and length(recipients.to) <= 1
and all(recipients.to, .email.domain.valid == false)
and length(headers.reply_to) == 1
and headers.reply_to[0].email.domain.root_domain != sender.email.domain.root_domain
and profile.by_sender_email().prevalence == "new"
Detection logic
Scope: inbound message.
Message sent to an invalid recipient domain with a reply-to address that differs from the sender address, originating from a new sender.
- inbound message
- length(recipients.to) ≤ 1
all of
recipients.towhere:- .email.domain.valid is False
- length(headers.reply_to) is 1
- headers.reply_to[0].email.domain.root_domain is not sender.email.domain.root_domain
- profile.by_sender_email().prevalence is 'new'
Inspects: headers.reply_to, headers.reply_to[0].email.domain.root_domain, recipients.to, recipients.to[].email.domain.valid, sender.email.domain.root_domain, type.inbound. Sensors: profile.by_sender_email.