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[DRAFT] Optimize phishing_blue_button_file_sharing #4804

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thunderkatz wants to merge 4 commits into from
+32 −46
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[DRAFT] Optimize phishing_blue_button_file_sharing #4804

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1b8a0e2
Match blue-button style via xpath predicate instead of regex over ful…
thunderkatz Jul 6, 2026
03cbba5
Simplify redundant no-previous-threads/fake-thread condition
thunderkatz Jul 6, 2026
2183043
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thunderkatz Jul 6, 2026
c06be6a
Auto-format MQL and add rule IDs
Jul 6, 2026
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78 changes: 32 additions & 46 deletions detection-rules/phishing_blue_button_file_sharing.yml
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Original file line number Diff line number Diff line change
Expand Up @@ -5,54 +5,41 @@ severity: "low"
source: |
type.inbound
and (
// no previous threads
// no previous threads, or no thread references at all
length(body.previous_threads) == 0
// or is a fake thread
or (
(length(headers.references) == 0 or headers.in_reply_to is null)
and (
subject.is_reply
or subject.is_forward
or length(body.previous_threads) > 0
)
)
or length(headers.references) == 0
or headers.in_reply_to is null
)
and any(filter(html.xpath(body.html, '//a[@href]').nodes,
// blue button background, background-color and observed colors
regex.icontains(.raw,
'(?:background(?:-color)?)\s*[:\s]\s*#(?:0078d4|3a78d1)'
)
),
(
// it's styled as a button
regex.icontains(.raw, 'padding')
)
and any(html.xpath(body.html,
// blue button background or background-color and observed colors, plus padding for button styling
'//a[@href][contains(translate(@style,"ABCDEFGHIJKLMNOPQRSTUVWXYZ","abcdefghijklmnopqrstuvwxyz"),"background") and (contains(translate(@style,"ABCDEFGHIJKLMNOPQRSTUVWXYZ","abcdefghijklmnopqrstuvwxyz"),"0078d4") or contains(translate(@style,"ABCDEFGHIJKLMNOPQRSTUVWXYZ","abcdefghijklmnopqrstuvwxyz"),"3a78d1")) and contains(translate(@style,"ABCDEFGHIJKLMNOPQRSTUVWXYZ","abcdefghijklmnopqrstuvwxyz"),"padding")]'
).nodes,
// ignore links going to microsoft
and not any(.links,
(
.href_url.domain.sld in (
"microsoft",
"azure",
"outlook.office365",
"office365"
)
)
or .href_url.domain.domain in $tenant_domains
or (
.href_url.domain.root_domain in (
"mimecast.com",
"mimecastprotect.com"
)
and any(.href_url.query_params_decoded['domain'],
strings.parse_domain(.).domain in (
"microsoft.com",
"azure.com",
"outlook.office365.com",
"office365.com"
)
or strings.parse_domain(.).domain in $tenant_domains
)
)
not any(.links,
(
.href_url.domain.sld in (
"microsoft",
"azure",
"outlook.office365",
"office365"
)
)
or .href_url.domain.domain in $tenant_domains
or (
.href_url.domain.root_domain in (
"mimecast.com",
"mimecastprotect.com"
)
and any(.href_url.query_params_decoded['domain'],
strings.parse_domain(.).domain in (
"microsoft.com",
"azure.com",
"outlook.office365.com",
"office365.com"
)
or strings.parse_domain(.).domain in $tenant_domains
)
)
)
)
and any(ml.nlu_classifier(body.current_thread.text).intents, .name != "benign")
Expand All @@ -65,7 +52,6 @@ source: |
sender.email.domain.root_domain == "microsoft.com"
and headers.auth_summary.dmarc.pass
)

attack_types:
- "Credential Phishing"
tactics_and_techniques:
Expand Down