Defense Evasion (TA0005)(external, opens in a new tab or window)
text code block:FROM logs-endpoint.events.process-* METADATA _id, _index, _version, _ignored | MV_EXPAND _ignored | WHERE _ignored == "process.command_line" | WHERE event.category == "process" and event.type == "start" | EVAL command_line = TO_LOWER(process.command_line.text), pname = TO_LOWER(process.name) | WHERE ( ( /* Python: inline exec with base64 decode or -c flag with encoded payload */ pname like "python*" and ( command_line like "*b64decode*" or (command_line like "*-c*" and command_line like "*base64*") ) ) or ( /* PowerShell: encoded command flag — require trailing space to avoid matching -Encoding, -EncryptionType, -EncryptionProvider, etc. */ (pname like "powershell*" or pname like "pwsh*") and ( command_line rlike ".* -(e|en|enc|enco|encod|encode|encoded|encodedcommand) .+" or command_line like "*-encodedcommand*" or command_line like "*frombase64string*" ) ) or ( /* Node.js: buffer.from must be paired with base64 to avoid matching general Buffer usage; atob is always base64 */ pname like "node*" and ( (command_line like "*buffer.from*" and command_line like "*base64*") or command_line like "*atob(*" ) ) or ( /* Deno: eval( (not eval/evaluate/evaluation), atob, or buffer+base64 */ pname like "deno*" and ( command_line like "*atob(*" or (command_line like "*buffer.from*" and command_line like "*base64*") or command_line like "*eval(*" ) ) ) | EVAL Esql.length_cmdline = LENGTH(command_line) | WHERE Esql.length_cmdline >= 4000 | KEEP *
Install detection rules in Elastic Security
Detect Long Base64 Encoded Command via Scripting Interpreter in the Elastic Security detection engine by installing this rule into your Elastic Stack.
To setup this rule, check out the installation guide for Prebuilt Security Detection Rules(external, opens in a new tab or window).