Add DecompressEXE signature for memory analysis

modules/signatures/windows/packer_decompress_buffer.py

@@ -0,0 +1,47 @@
+# Copyright (C) 2026 Kevin Ross
+#
+# 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 DecompressEXE(Signature):
+    name = "decompress_exe"
+    description = "Decompresses an executable in memory, may be indicative of a packer or manual loader"
+    severity = 2
+    confidence = 50
+    categories = ["packer"]
+    authors = ["Kevin Ross"]
+    minimum = "1.3"
+    evented = True
+    enabled = True
+    ttps = ["T1027", "T1027.002", "T1620"] 
+    mbcs = ["B0002", "F0001", "OB0006"]
+
+    filter_apinames = set(["RtlDecompressBuffer"])
+
+    def __init__(self, *args, **kwargs):
+        Signature.__init__(self, *args, **kwargs)
+        self.ret = False
+
+    def on_call(self, call, process):
+        if not call["status"]:
+            return None
+        if call["api"] == "RtlDecompressBuffer":
+            buf = self.get_argument(call, "UncompressedBuffer")
+            if buf and buf.startswith("MZ"):
+                self.ret = True
+                self.mark_call()    
+
+    def on_complete(self):
+        return self.ret