Detection rules › Sublime MQL
Callback phishing solicitation in message body
A fraudulent invoice/receipt found in the body of the message. Callback phishing is an attempt by an attacker to solicit the victim (recipient) to call a phone number. The resulting interaction could lead to a multitude of attacks ranging from Financial theft, Remote Access Trojan (RAT) Installation or Ransomware Deployment.
Threat classification
Sublime's own taxonomy (not MITRE ATT&CK).
| Category | Values |
|---|---|
| Attack types | Callback Phishing |
| Tactics and techniques | Free email provider, Impersonation: Brand, Out of band pivot, Social engineering |
Event coverage
Rule body MQL
type.inbound
and length(attachments) == 0
and (
not profile.by_sender().solicited
or (
profile.by_sender().any_messages_malicious_or_spam
and not profile.by_sender().any_messages_benign
)
)
and (
sender.email.domain.root_domain in $free_email_providers
or sender.email.domain.tld in $suspicious_tlds
or network.whois(sender.email.domain).found == false
or headers.mailer in~ ("Microsoft CDO for Windows 2000")
or (
length(recipients.to) == 1
and all(recipients.to, .email.domain.domain not in $org_domains)
)
)
and (
// this section is synced with attachment_callback_phish_with_pdf.yml and attachment_callback_phish_with_img.yml
regex.icontains(body.current_thread.text,
'(p.{0,3}a.{0,3}y.{0,3}p.{0,3}a.{0,3}l|ma?c.?fee|n[o0]rt[o0]n|geek.{0,5}squad|ebay|symantec|best buy|lifel[o0]c|secure anywhere|starz|utilities premium|pc security|at&t)'
)
or any(ml.logo_detect(file.message_screenshot()).brands,
.name in ("PayPal", "Norton", "GeekSquad", "Ebay", "McAfee", "AT&T")
)
//
// This rule makes use of a beta feature and is subject to change without notice
// using the beta feature in custom rules is not suggested until it has been formally released
//
or regex.icontains(beta.ocr(file.message_screenshot()).text,
'(p.{0,3}a.{0,3}y.{0,3}p.{0,3}a.{0,3}l|ma?c.?fee|n[o0]rt[o0]n|geek.{0,5}squad|ebay|symantec|best buy|lifel[o0]c|secure anywhere|starz|utilities premium|pc security|at&t)'
)
)
and length(body.current_thread.text) < 1750
and (
(
// this seciton is synced with attachment_callback_phish_with_img.yml and attachment_callback_phish_with_pdf.yml
// however, the 3 of logic and requiring a phone number is specific to this rule in order to reduce FPs
// caused by messages which mention cancelling or otherwise managing a subscription
// it is also synced and below for message_screenshot OCR output
3 of (
strings.icontains(body.current_thread.text, 'purchase'),
strings.icontains(body.current_thread.text, 'payment'),
strings.icontains(body.current_thread.text, 'transaction'),
strings.icontains(body.current_thread.text, 'subscription'),
strings.icontains(body.current_thread.text, 'antivirus'),
strings.icontains(body.current_thread.text, 'order'),
strings.icontains(body.current_thread.text, 'support'),
strings.icontains(body.current_thread.text, 'help line'),
strings.icontains(body.current_thread.text, 'receipt'),
strings.icontains(body.current_thread.text, 'invoice'),
strings.icontains(body.current_thread.text, 'call'),
strings.icontains(body.current_thread.text, 'cancel'),
strings.icontains(body.current_thread.text, 'renew'),
strings.icontains(body.current_thread.text, 'refund'),
regex.icontains(body.current_thread.text, "(?:reach|contact) us at"),
strings.icontains(body.current_thread.text, "+1"),
strings.icontains(body.current_thread.text, "amount"),
strings.icontains(body.current_thread.text, "charged"),
strings.icontains(body.current_thread.text, "crypto"),
strings.icontains(body.current_thread.text, "wallet address"),
regex.icontains(body.current_thread.text, '\$\d{3}\.\d{2}\b'),
)
// phone number regex
and regex.icontains(body.current_thread.text,
'\+?([ilo0-9]{1}.)?\(?[ilo0-9]{3}?\)?.[ilo0-9]{3}.?[ilo0-9]{4}',
'\+?([ilo0-9]{1,2})?\s?\(?\d{3}\)?[\s\.\-⋅]{0,5}[ilo0-9]{3}[\s\.\-⋅]{0,5}[ilo0-9]{4}'
)
)
or (
any(file.explode(file.message_screenshot()),
// this seciton is synced with attachment_callback_phish_with_img.yml and attachment_callback_phish_with_pdf.yml
// and above for current_thread.text
3 of (
strings.icontains(.scan.ocr.raw, 'purchase'),
strings.icontains(.scan.ocr.raw, 'payment'),
strings.icontains(.scan.ocr.raw, 'transaction'),
strings.icontains(.scan.ocr.raw, 'subscription'),
strings.icontains(.scan.ocr.raw, 'antivirus'),
strings.icontains(.scan.ocr.raw, 'order'),
strings.icontains(.scan.ocr.raw, 'support'),
strings.icontains(.scan.ocr.raw, 'help line'),
strings.icontains(.scan.ocr.raw, 'receipt'),
strings.icontains(.scan.ocr.raw, 'invoice'),
strings.icontains(.scan.ocr.raw, 'call'),
strings.icontains(.scan.ocr.raw, 'helpdesk'),
strings.icontains(.scan.ocr.raw, 'cancel'),
strings.icontains(.scan.ocr.raw, 'renew'),
strings.icontains(.scan.ocr.raw, 'refund'),
regex.icontains(.scan.ocr.raw, "(?:reach|contact) us at"),
strings.icontains(.scan.ocr.raw, '+1'),
strings.icontains(.scan.ocr.raw, 'amount'),
strings.icontains(.scan.ocr.raw, 'charged'),
strings.icontains(.scan.ocr.raw, 'crypto'),
strings.icontains(.scan.ocr.raw, 'wallet address'),
regex.icontains(.scan.ocr.raw, '\$\d{3}\.\d{2}\b'),
)
// phone number regex
and regex.icontains(.scan.ocr.raw,
'\+?([ilo0-9]{1}.)?\(?[ilo0-9]{3}?\)?.[ilo0-9]{3}.?[ilo0-9]{4}',
'\+?([ilo0-9]{1,2})?\s?\(?\d{3}\)?[\s\.\-⋅]{0,5}[ilo0-9]{3}[\s\.\-⋅]{0,5}[ilo0-9]{4}'
)
// negate messages with previous threads. While callback phishing with thread hijacking or with current_thread
// padded with whitespace and previous threads in the message has been observed, the intetion of using OCR is for image embedded callbacks
and not regex.icount(.scan.ocr.raw, '(?:from|to|sent|date|cc|subject):') > 3
// this notation of previous threads often only occurs once
and not regex.icontains(.scan.ocr.raw, 'wrote:[\r\n]')
)
)
)
// not high trust sender 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
)
and not strings.ends_with(headers.message_id, "@shopify.com>")
Detection logic
Scope: inbound message.
A fraudulent invoice/receipt found in the body of the message. Callback phishing is an attempt by an attacker to solicit the victim (recipient) to call a phone number. The resulting interaction could lead to a multitude of attacks ranging from Financial theft, Remote Access Trojan (RAT) Installation or Ransomware Deployment.
- inbound message
- length(attachments) is 0
any of:
not:
- profile.by_sender().solicited
all of:
- profile.by_sender().any_messages_malicious_or_spam
not:
- profile.by_sender().any_messages_benign
any of:
- sender.email.domain.root_domain in $free_email_providers
- sender.email.domain.tld in $suspicious_tlds
- network.whois(sender.email.domain).found is False
- headers.mailer in ('Microsoft CDO for Windows 2000')
all of:
- length(recipients.to) is 1
all of
recipients.towhere:- .email.domain.domain not in $org_domains
any of:
- body.current_thread.text matches '(p.{0,3}a.{0,3}y.{0,3}p.{0,3}a.{0,3}l|ma?c.?fee|n[o0]rt[o0]n|geek.{0,5}squad|ebay|symantec|best buy|lifel[o0]c|secure anywhere|starz|utilities premium|pc security|at&t)'
any of
ml.logo_detect(file.message_screenshot()).brandswhere:- .name in ('PayPal', 'Norton', 'GeekSquad', 'Ebay', 'McAfee', 'AT&T')
- beta.ocr(file.message_screenshot()).text matches '(p.{0,3}a.{0,3}y.{0,3}p.{0,3}a.{0,3}l|ma?c.?fee|n[o0]rt[o0]n|geek.{0,5}squad|ebay|symantec|best buy|lifel[o0]c|secure anywhere|starz|utilities premium|pc security|at&t)'
- length(body.current_thread.text) < 1750
any of:
all of:
at least 3 of:
- body.current_thread.text contains 'purchase'
- body.current_thread.text contains 'payment'
- body.current_thread.text contains 'transaction'
- body.current_thread.text contains 'subscription'
- body.current_thread.text contains 'antivirus'
- body.current_thread.text contains 'order'
- body.current_thread.text contains 'support'
- body.current_thread.text contains 'help line'
- body.current_thread.text contains 'receipt'
- body.current_thread.text contains 'invoice'
- body.current_thread.text contains 'call'
- body.current_thread.text contains 'cancel'
- body.current_thread.text contains 'renew'
- body.current_thread.text contains 'refund'
- body.current_thread.text matches '(?:reach|contact) us at'
- body.current_thread.text contains '+1'
- body.current_thread.text contains 'amount'
- body.current_thread.text contains 'charged'
- body.current_thread.text contains 'crypto'
- body.current_thread.text contains 'wallet address'
- body.current_thread.text matches '\\$\\d{3}\\.\\d{2}\\b'
body.current_thread.text matches any of 2 patterns
\+?([ilo0-9]{1}.)?\(?[ilo0-9]{3}?\)?.[ilo0-9]{3}.?[ilo0-9]{4}\+?([ilo0-9]{1,2})?\s?\(?\d{3}\)?[\s\.\-⋅]{0,5}[ilo0-9]{3}[\s\.\-⋅]{0,5}[ilo0-9]{4}
any of
file.explode(...)where all hold:at least 3 of:
- .scan.ocr.raw contains 'purchase'
- .scan.ocr.raw contains 'payment'
- .scan.ocr.raw contains 'transaction'
- .scan.ocr.raw contains 'subscription'
- .scan.ocr.raw contains 'antivirus'
- .scan.ocr.raw contains 'order'
- .scan.ocr.raw contains 'support'
- .scan.ocr.raw contains 'help line'
- .scan.ocr.raw contains 'receipt'
- .scan.ocr.raw contains 'invoice'
- .scan.ocr.raw contains 'call'
- .scan.ocr.raw contains 'helpdesk'
- .scan.ocr.raw contains 'cancel'
- .scan.ocr.raw contains 'renew'
- .scan.ocr.raw contains 'refund'
- .scan.ocr.raw matches '(?:reach|contact) us at'
- .scan.ocr.raw contains '+1'
- .scan.ocr.raw contains 'amount'
- .scan.ocr.raw contains 'charged'
- .scan.ocr.raw contains 'crypto'
- .scan.ocr.raw contains 'wallet address'
- .scan.ocr.raw matches '\\$\\d{3}\\.\\d{2}\\b'
.scan.ocr.raw matches any of 2 patterns
\+?([ilo0-9]{1}.)?\(?[ilo0-9]{3}?\)?.[ilo0-9]{3}.?[ilo0-9]{4}\+?([ilo0-9]{1,2})?\s?\(?\d{3}\)?[\s\.\-⋅]{0,5}[ilo0-9]{3}[\s\.\-⋅]{0,5}[ilo0-9]{4}
not:
- regex.icount(.scan.ocr.raw, '(?:from|to|sent|date|cc|subject):') > 3
not:
- .scan.ocr.raw matches 'wrote:[\\r\\n]'
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
not:
- headers.message_id ends with '@shopify.com>'
Inspects: body.current_thread.text, headers.auth_summary.dmarc.pass, headers.mailer, headers.message_id, recipients.to, recipients.to[].email.domain.domain, sender.email.domain, sender.email.domain.root_domain, sender.email.domain.tld, type.inbound. Sensors: beta.ocr, file.explode, file.message_screenshot, ml.logo_detect, network.whois, profile.by_sender, regex.icontains, regex.icount, strings.ends_with, strings.icontains. Reference lists: $free_email_providers, $high_trust_sender_root_domains, $org_domains, $suspicious_tlds.
Indicators matched (35)
| Field | Match | Value |
|---|---|---|
headers.mailer | member | Microsoft CDO for Windows 2000 |
regex.icontains | regex | (p.{0,3}a.{0,3}y.{0,3}p.{0,3}a.{0,3}l|ma?c.?fee|n[o0]rt[o0]n|geek.{0,5}squad|ebay|symantec|best buy|lifel[o0]c|secure anywhere|starz|utilities premium|pc security|at&t) |
ml.logo_detect(file.message_screenshot()).brands[].name | member | PayPal |
ml.logo_detect(file.message_screenshot()).brands[].name | member | Norton |
ml.logo_detect(file.message_screenshot()).brands[].name | member | GeekSquad |
ml.logo_detect(file.message_screenshot()).brands[].name | member | Ebay |
ml.logo_detect(file.message_screenshot()).brands[].name | member | McAfee |
ml.logo_detect(file.message_screenshot()).brands[].name | member | AT&T |
strings.icontains | substring | purchase |
strings.icontains | substring | payment |
strings.icontains | substring | transaction |
strings.icontains | substring | subscription |
23 more
strings.icontains | substring | antivirus |
strings.icontains | substring | order |
strings.icontains | substring | support |
strings.icontains | substring | help line |
strings.icontains | substring | receipt |
strings.icontains | substring | invoice |
strings.icontains | substring | call |
strings.icontains | substring | cancel |
strings.icontains | substring | renew |
strings.icontains | substring | refund |
regex.icontains | regex | (?:reach|contact) us at |
strings.icontains | substring | +1 |
strings.icontains | substring | amount |
strings.icontains | substring | charged |
strings.icontains | substring | crypto |
strings.icontains | substring | wallet address |
regex.icontains | regex | \$\d{3}\.\d{2}\b |
regex.icontains | regex | \+?([ilo0-9]{1}.)?\(?[ilo0-9]{3}?\)?.[ilo0-9]{3}.?[ilo0-9]{4} |
regex.icontains | regex | \+?([ilo0-9]{1,2})?\s?\(?\d{3}\)?[\s\.\-⋅]{0,5}[ilo0-9]{3}[\s\.\-⋅]{0,5}[ilo0-9]{4} |
strings.icontains | substring | helpdesk |
regex.icount | regex | (?:from|to|sent|date|cc|subject): |
regex.icontains | regex | wrote:[\r\n] |
strings.ends_with | suffix | @shopify.com> |