Create sig for likely ransomware asynchronous encryption

modules/signatures/windows/ransomware_asynchronous_encryption.py

@@ -0,0 +1,60 @@
+# Copyright (C) 2026 Kevin Ross, identification of the behavior covered in this signature and some of the signature was generated by Gemini
+#
+# This program is free software: you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+from lib.cuckoo.common.abstracts import Signature
+
+class RansomwareIOCPAsynchronousEncryption(Signature):
+    name = "ransomware_iocp_asynchronous_encryption"
+    description = "Binds a large number of files to I/O Completion Ports (IOCP), possible ransomware asynchronous encryption"
+    severity = 4
+    confidence = 80
+    categories = ["ransomware"]
+    authors = ["Kevin Ross", "Gemini"]
+    minimum = "1.3"
+    evented = True
+    ttps = ["T1486"]
+
+    filter_apinames = {"NtSetInformationFile"}
+
+    def __init__(self, *args, **kwargs):
+        Signature.__init__(self, *args, **kwargs)
+        self.iocp_files = set()
+        self.example_file = None
+
+    def on_call(self, call, process):
+        info_class = self.get_argument(call, "FileInformationClass")
+
+        if info_class == 30 or str(info_class) == "30" or str(info_class).upper() == "FILECOMPLETIONINFORMATION":
+            filepath = self.get_argument(call, "HandleName")
+
+            if isinstance(filepath, str) and "\\" in filepath:
+                filepath_lower = filepath.lower()
+
+                # Ignore system devices/pipes
+                if "\\??\\" in filepath_lower or "\\device\\" in filepath_lower:
+                    return
+
+                if filepath_lower not in self.iocp_files:                       
+                    self.iocp_files.add(filepath_lower)                   
+                    if len(self.iocp_files) <= 15:
+                        self.mark_call()
+
+    def on_complete(self):
+        if len(self.iocp_files) > 50:
+            self.data.append({
+                "total_files_bound_to_iocp": len(self.iocp_files),
+            })
+            return True
+        return False