From 0323b126dac75749737f95c1b93f2190c4a753ec Mon Sep 17 00:00:00 2001
From: Aiden Mitchell <me@aidenmitchell.ca>
Date: Wed, 6 Dec 2023 10:18:08 -0800
Subject: [PATCH 1/2] New rule: invoicera_infra_abuse.yml

---
 detection-rules/invoicera_infra_abuse.yml | 43 +++++++++++++++++++++++
 1 file changed, 43 insertions(+)
 create mode 100644 detection-rules/invoicera_infra_abuse.yml

diff --git a/detection-rules/invoicera_infra_abuse.yml b/detection-rules/invoicera_infra_abuse.yml
new file mode 100644
index 00000000000..d0b6df3a18d
--- /dev/null
+++ b/detection-rules/invoicera_infra_abuse.yml
@@ -0,0 +1,43 @@
+name: "Invoicera infrastructure abuse"
+description: "This rule is tailored to flag infrastructural abuse involving Invoicera, a SaaS-based invoicing and billing platform, which has been identified as a tool in widespread spam and credential phishing campaigns."
+type: "rule"
+severity: "medium"
+source: |
+  type.inbound
+  and sender.email.domain.root_domain == "invoicera.com"
+  // suspicious recipient pattern
+  and (
+    length(recipients.to) == 0
+    or any(recipients.to, .email.domain.valid == false)
+    or length(recipients.bcc) > 0
+  )
+  // suspicious link
+  and (
+    any(body.links,
+        .href_url.domain.root_domain in $free_file_hosts
+        or .href_url.domain.domain in $free_file_hosts
+    )
+    or any(body.links,
+           .href_url.domain.root_domain in $free_subdomain_hosts
+           and .href_url.domain.subdomain is not null
+           and .href_url.domain.subdomain != "www"
+    )
+  )
+  // mismatched reply-to
+  and (
+    headers.return_path.email is not null
+    and headers.return_path.email != sender.email.email
+  )
+
+attack_types:
+  - "Credential Phishing"
+  - "Spam"
+tactics_and_techniques:
+  - "Free file host"
+  - "Free subdomain host"
+  - "Image as content"
+  - "Social engineering"
+detection_methods:
+  - "Content analysis"
+  - "Header analysis"
+  - "Sender analysis"

From ac8002e3e69e085313cba8015e2de4b04048f4ec Mon Sep 17 00:00:00 2001
From: ID Generator <hello@sublimesecurity.com>
Date: Wed, 6 Dec 2023 18:21:28 +0000
Subject: [PATCH 2/2] Auto add rule ID

---
 detection-rules/invoicera_infra_abuse.yml | 1 +
 1 file changed, 1 insertion(+)

diff --git a/detection-rules/invoicera_infra_abuse.yml b/detection-rules/invoicera_infra_abuse.yml
index d0b6df3a18d..d81e0f671d3 100644
--- a/detection-rules/invoicera_infra_abuse.yml
+++ b/detection-rules/invoicera_infra_abuse.yml
@@ -41,3 +41,4 @@ detection_methods:
   - "Content analysis"
   - "Header analysis"
   - "Sender analysis"
+id: "1e56f310-750b-5c26-84eb-63e78f20a6bd"