Shellcode Behavior from Unusual Memory

[rule]
description = "Identifies when a process attempts to allocate shellcode from a memory with unusual properties."
id = "4fd32c09-dcb8-442c-a5ac-b8f3f98ffe6c"
license = "Elastic License v2"
name = "Shellcode Behavior from Unusual Memory"
os_list = ["windows"]
version = "1.0.4"

query = '''
api where process.Ext.api.behaviors in ("allocate_shellcode", "shellcode", "hollow_unbacked", "execute_fluctuation") and
 process.thread.Ext.call_stack_final_user_module.protection in ("RW-", "R--", "---") and process.thread.Ext.call_stack_final_user_module.name == "Unbacked" and
 process.Ext.api.name in ("VirtualAlloc", "VirtualProtect", "WriteProcessMemory", "VirtualProtectEx", "VirtualAllocEx",
                          "MapViewOfFile", "MapViewOfFile2", "SetThreadContext", "SuspendThread", "ReadProcessMemory", "connect") and
 not _arraysearch(process.thread.Ext.call_stack_final_user_module.code_signature, $entry, $entry.trusted == true and not $entry.subject_name in ("Microsoft Corporation", "Microsoft Windows")) and
 not (process.executable : "C:\\Windows\\System32\\WindowsPowerShell\\1.0\\powershell.exe" and process.Ext.api.behaviors == "hollow_unbacked" and
      process.thread.Ext.call_stack_final_user_module.protection_provenance_path like "c:\\windows\\assembly\\nativeimages_*.ni.dll") and
 not (process.Ext.api.name == "VirtualProtect" and _arraysearch(process.thread.Ext.call_stack, $entry, $entry.symbol_info like ("*kernelbase.dll!LoadLibrary*", "*kernel32.dll!ExitProcess*"))) and
 process.thread.Ext.call_stack_final_user_module.hash.sha256 != "6a6f026505c3701e03b065ec38e64b105ff6b7129c249a77b45ad4c59d593e26" and
 not (process.executable : "C:\\Windows\\System32\\dllhost.exe" and process.parent.executable : "C:\\Windows\\System32\\svchost.exe" and
      process.thread.Ext.call_stack_summary == "ntdll.dll|kernelbase.dll|dbgeng.dll|Unbacked|Unknown" and
      process.thread.Ext.call_stack_final_user_module.protection_provenance_path == "c:\\windows\\system32\\msmpeg2adec.dll") and
 not (process.executable : "C:\\Program Files (x86)\\Mozilla Firefox\\firefox.exe" and process.thread.Ext.call_stack_final_user_module.protection_provenance_path == "c:\\windows\\syswow64\\d3d9.dll") and
 not (process.executable : "C:\\Program Files\\Epic Games\\Fortnite\\FortniteGame\\Binaries\\Win64\\FortniteClient-Win64-Shipping.exe" and
      process.code_signature.subject_name == "Epic Games Inc." and process.code_signature.trusted == true)
'''

min_endpoint_version = "8.14.2"
optional_actions = []
[[actions]]
action = "kill_process"
field = "process.entity_id"
state = 0
tree = true

[[threat]]
framework = "MITRE ATT&CK"
[[threat.technique]]
id = "T1055"
name = "Process Injection"
reference = "https://attack.mitre.org/techniques/T1055/"


[threat.tactic]
id = "TA0005"
name = "Defense Evasion"
reference = "https://attack.mitre.org/tactics/TA0005/"

[internal]
min_endpoint_version = "8.14.2"