diff --git a/modules/signatures/windows/antiedr_syscall.py b/modules/signatures/windows/antiedr_syscall.py new file mode 100644 index 00000000..8e670dda --- /dev/null +++ b/modules/signatures/windows/antiedr_syscall.py @@ -0,0 +1,69 @@ +# Copyright (C) 2025 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 . + +from lib.cuckoo.common.abstracts import Signature + + +class Suspicious_NTDLL_DiskLoad(Signature): + name = "suspicious_ntdll_disk_load" + description = "Loads clean ntdll.dll from disk (possibly for syscall/anti-EDR)" + severity = 3 + categories = ["syscall", "anti-edr", "unhooking"] + authors = ["Kevin Ross"] + minimum = "1.3" + evented = True + ttps = ["T1106"] # MITRE v6,7,8 + + filter_apinames = set(["NtCreateFile", "NtCreateSection", "NtOpenFile", "NtProtectVirtualMemory", "NtReadFile"]) + + def __init__(self, *args, **kwargs): + Signature.__init__(self, *args, **kwargs) + self.ret = False + self.filehandle = "" + self.mapped = False + + def on_call(self, call, process): + if call["api"] in ["NtCreateFile", "NtOpenFile"]: + filename = self.get_argument(call, "FileName") + if filename and filename.lower().endswith(r"\system32\ntdll.dll"): + filehandle = self.get_argument(call, "FileHandle") + self.filehandle = filehandle + self.mark_call() + self.ret = True + + if call["api"] == ("NtReadFile"): + filehandle = self.get_argument(call, "FileHandle") + handlename = self.get_argument(call, "HandleName") + if self.filehandle and filehandle == self.filehandle and handlename and "ntdll.dll" in handlename.lower(): + self.mark_call() + + if call["api"] == ("NtCreateSection"): + filehandle = self.get_argument(call, "FileHandle") + filename = self.get_argument(call, "FileName") + if filehandle == self.filehandle and "ntdll.dll" in filename.lower(): + self.mapped = True + self.mark_call() + + if call["api"] == ("NtProtectVirtualMemory"): + if self.mapped: + modulename = self.get_argument(call, "ModuleName") + if modulename and modulename.lower() == "ntdll.dll": + protection = self.get_argument(call, "NewAccessProtection") + # 0x40 PAGE_EXECUTE_READWRITE, 0x80 PAGE_EXECUTE_WRITECOPY, 0x04 PAGE_READWRITE + if protection in ["0x00000040", "0x00000080", "0x00000004"]: + self.mark_call() + + def on_complete(self): + return self.ret