Elastic Defend high stable eql
Suspicious Call Stack Trailing Bytes
Identifies API or library events with suspicious call stack trailing bytes often related to shellcode execution.
Detection Logic
any where process.executable != null and
/* add esp, 0xab; ret; nop; nop; nop; */
_arraysearch(process.thread.Ext.call_stack, $entry, $entry.callsite_trailing_bytes : ("4883????c3909090909090*", "4883C4485B415CC390909090*")) and
(
(event.category == "api" and process.Ext.api.name like ("VirtualProtect*", "WriteProcessMemory")) or
(event.category == "library" and dll.name in~ ("ws2_32.dll", "wininet.dll", "winhttp.dll"))
) and
not _arraysearch(process.thread.Ext.call_stack, $entry,
$entry.callsite_trailing_bytes :
("4883c428c390909090909090904c8bdc574883ec6049c743b8feffffff49895b1849897320488b05c9a024004833c44889442450488bfa488bd9488b521849c7",
"4883c4205bc3488b8180000000c390909090909090904883ec2833c08b123b15261b3601751d83797c007417488b05f3d43101488b008b517c4889c1e8c5a406",
"4883c428c3909090909090909090909044894c242044894424188954241048894c24084883ec28*")) and
not _arraysearch(process.thread.Ext.call_stack, $entry,
$entry.callsite_leading_bytes :"3b4208750b498908488b01ff5008eb05bb024000808bc34883c4205bc34883ec3848c7442420feffffff488bc1488b094885c9740b48832000488b01ff501090") Field Validations
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