From f7735df1d578128d1fb8a1bb883349fb54129751 Mon Sep 17 00:00:00 2001
From: shashank-elastic <91139415+shashank-elastic@users.noreply.github.com>
Date: Wed, 16 Mar 2022 23:06:34 +0530
Subject: [PATCH] [New Rule] c89/c99 shell evasion threat (#1840)

* c88/c99 shell evasion threat
---
 rules/linux/execution_c89_c99_binary.toml | 51 +++++++++++++++++++++++
 1 file changed, 51 insertions(+)
 create mode 100644 rules/linux/execution_c89_c99_binary.toml

diff --git a/rules/linux/execution_c89_c99_binary.toml b/rules/linux/execution_c89_c99_binary.toml
new file mode 100644
index 000000000..c3103f358
--- /dev/null
+++ b/rules/linux/execution_c89_c99_binary.toml
@@ -0,0 +1,51 @@
+[metadata]
+creation_date = "2022/03/15"
+maturity = "production"
+updated_date = "2022/03/15"
+
+[rule]
+author = ["Elastic"]
+description = """
+Identifies Linux binary c89/c99 abuse to break out from restricted environments by spawning an interactive system
+shell.The c89/c99 utility is an interface to the standard C compilation system and the activity of spawing a shell is
+not a standard use of this binary by a user or system administrator. It indicates a potentially 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 c89/c99 Shell evasion"
+references = ["https://gtfobins.github.io/gtfobins/c89/", "https://gtfobins.github.io/gtfobins/c99/"]
+risk_score = 47
+rule_id = "1859ce38-6a50-422b-a5e8-636e231ea0cd"
+severity = "medium"
+tags = ["Elastic", "Host", "Linux", "Threat Detection", "Execution", "GTFOBins"]
+timestamp_override = "event.ingested"
+type = "eql"
+
+query = '''
+sequence by host.id, process.pid with maxspan=1m
+[process where process.name :("c89","c99") 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 : ("bash", "sh", "dash")]
+'''
+
+
+[[rule.threat]]
+framework = "MITRE ATT&CK"
+[[rule.threat.technique]]
+id = "T1059"
+name = "Command and Scripting Interpreter"
+reference = "https://attack.mitre.org/techniques/T1059/"
+[[rule.threat.technique.subtechnique]]
+id = "T1059.004"
+name = "Unix Shell"
+reference = "https://attack.mitre.org/techniques/T1059/004/"
+
+
+
+[rule.threat.tactic]
+id = "TA0002"
+name = "Execution"
+reference = "https://attack.mitre.org/tactics/TA0002/"
+