gcc shell evasion threat (#1824)

rules/linux/defense_evasion_gcc_binary.toml

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+[metadata]
+creation_date = "2022/03/09"
+maturity = "production"
+updated_date = "2022/03/09"
+
+[rule]
+author = ["Elastic"]
+description = """
+Identifies Linux binary gcc abuse to break out from restricted environments by spawning an interactive system shell.This
+activity is not standard use with this binary for a user or system administrator and could potentially indicate
+malicious actor attempting to improve the capabilities or stability of their access.
+"""
+from = "now-9m"
+index = ["logs-endpoint.events.*"]
+language = "eql"
+license = "Elastic License v2"
+name = "Linux Restricted Shell Breakout via the gcc command"
+references = ["https://gtfobins.github.io/gtfobins/gcc/"]
+risk_score = 47
+rule_id = "da986d2c-ffbf-4fd6-af96-a88dbf68f386"
+severity = "medium"
+tags = ["Elastic", "Host", "Linux", "Threat Detection", "Defense Evasion", "GTFOBins"]
+timestamp_override = "event.ingested"
+type = "eql"
+
+query = '''
+sequence by host.id, process.pid with maxspan=1m
+[process where process.name == "gcc" and process.args == "-wrapper" and process.args : ("sh,-s", "bash,-s", "dash,-s", "/bin/sh,-s", "/bin/bash,-s", "/bin/dash,-s")]
+[process where process.parent.name == "gcc" and process.name : ("bash", "sh", "dash")]
+'''
+
+
+[[rule.threat]]
+framework = "MITRE ATT&CK"
+[[rule.threat.technique]]
+id = "T1548"
+name = "Abuse Elevation Control Mechanism"
+reference = "https://attack.mitre.org/techniques/T1548/"
+[[rule.threat.technique.subtechnique]]
+id = "T1548.004"
+name = "Elevated Execution with Prompt"
+reference = "https://attack.mitre.org/techniques/T1548/004/"
+
+
+
+[rule.threat.tactic]
+id = "TA0005"
+name = "Defense Evasion"
+reference = "https://attack.mitre.org/tactics/TA0005/"
+