New Rule: attachment_fake_slack_installer.yml (#837)

Co-authored-by: ID Generator <[email protected]>
Co-authored-by: Sam Scholten <[email protected]>

detection-rules/attachment_fake_slack_installer.yml

@@ -0,0 +1,62 @@
+name: "Attachment: Fake Slack installer"
+description: |
+  HTML attachment contains a Slack logo, request language, and a link to an executable. Observed in the wild.
+type: "rule"
+severity: "high"
+source: |
+  type.inbound
+  and (
+    any(attachments,
+        (
+          .file_extension in~ ("html", "htm", "shtml", "dhtml")
+          or .file_type == "html"
+          or .content_type == "text/html"
+        )
+        and any(file.explode(.),
+                any(ml.logo_detect(file.html_screenshot(..)).brands,
+                    .name == "Slack" and .confidence in ("medium", "high")
+                )
+                and any(ml.nlu_classifier(file.parse_html(..).display_text).entities,
+                        .name == "request" and .text =~ "download"
+                )
+                and any(.scan.url.urls,
+                        strings.iends_with(.path, ".exe") and .domain.root_domain not in $org_domains
+                )
+        )
+    )
+    or any(attachments,
+           (.file_extension in~ $file_extensions_common_archives)
+           and any(file.explode(.),
+                   (
+                     .file_extension in~ ("html", "htm", "shtml", "dhtml")
+                     or ..file_type == "html"
+                     or ..content_type == "text/html"
+                   )
+                   and any(ml.logo_detect(file.html_screenshot(..)).brands,
+                           .name == "Slack" and .confidence in ("medium", "high")
+                   )
+                   and any(ml.nlu_classifier(file.parse_html(..).display_text).entities,
+                           .name == "request" and .text =~ "download"
+                   )
+                   and any(.scan.url.urls,
+                           strings.iends_with(.path, ".exe") and .domain.root_domain not in $org_domains
+                   )
+           )
+    )
+  )
+attack_types:
+  - "Malware/Ransomware"
+tactics_and_techniques:
+  - "Evasion"
+  - "HTML smuggling"
+  - "Impersonation: Brand"
+  - "Scripting"
+  - "Social engineering"
+detection_methods:
+  - "Archive analysis"
+  - "Computer Vision"
+  - "File analysis"
+  - "HTML analysis"
+  - "Natural Language Understanding"
+  - "URL analysis"
+id: "cded2d2f-a5ca-5754-9f2a-d6bdf28baab4"