[Rule tuning] Linux binary(s) shell evasion threat (#1957)

* Linux binary(s) shell evasion threat

Co-authored-by: Samirbous <64742097+Samirbous@users.noreply.github.com>
Co-authored-by: Colson Wilhoit <48036388+DefSecSentinel@users.noreply.github.com>
Co-authored-by: Samirbous <64742097+Samirbous@users.noreply.github.com>
Co-authored-by: Terrance DeJesus <99630311+terrancedejesus@users.noreply.github.com>

rules/_deprecated/execution_apt_binary.toml

@@ -1,7 +1,8 @@
 [metadata]
 creation_date = "2022/02/24"
-maturity = "production"
-updated_date = "2022/03/31"
+deprecation_date = "2022/05/09"
+maturity = "deprecated"
+updated_date = "2022/05/09"
 
 [rule]
 author = ["Elastic"]

rules/_deprecated/execution_awk_binary_shell.toml

@@ -1,7 +1,8 @@
 [metadata]
 creation_date = "2022/02/24"
-maturity = "production"
-updated_date = "2022/03/31"
+deprecation_date = "2022/05/09"
+maturity = "deprecated"
+updated_date = "2022/05/09"
 
 [rule]
 author = ["Elastic"]

rules/_deprecated/execution_busybox_binary.toml

@@ -1,15 +1,16 @@
 [metadata]
 creation_date = "2022/03/15"
-maturity = "production"
-updated_date = "2022/03/24"
+deprecation_date = "2022/05/09"
+maturity = "deprecated"
+updated_date = "2022/05/09"
 
 [rule]
 author = ["Elastic"]
 description = """
 Identifies Linux binary busybox abuse to break out from restricted environments by spawning an interactive system
-shell.The busybox is software utility suite that provides several Unix utilities in a single executable file 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.
+shell.The busybox is software utility suite that provides several Unix utilities in a single executable file 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.*"]

rules/_deprecated/execution_c89_c99_binary.toml

@@ -1,7 +1,8 @@
 [metadata]
 creation_date = "2022/03/15"
-maturity = "production"
-updated_date = "2022/03/31"
+deprecation_date = "2022/05/09"
+maturity = "deprecated"
+updated_date = "2022/05/09"
 
 [rule]
 author = ["Elastic"]

rules/_deprecated/execution_cpulimit_binary.toml

@@ -1,7 +1,8 @@
 [metadata]
 creation_date = "2022/03/17"
-maturity = "production"
-updated_date = "2022/03/31"
+deprecation_date = "2022/05/09"
+maturity = "deprecated"
+updated_date = "2022/05/09"
 
 [rule]
 author = ["Elastic"]
@@ -9,8 +10,8 @@ description = """
 Identifies Linux binary cpulimit abuse to break out from restricted environments by spawning an interactive system
 shell. The cpulimit utility is used to restrict the CPU usage of a process in cases of CPU or system load exceeding the
 defined threshold and the activity of spawning a shell is not a standard use of this binary by a user or system
-administrator. This can potentially indicate a malicious actor attempting to improve the capabilities or stability of their
-access.
+administrator. This can potentially indicate a malicious actor attempting to improve the capabilities or stability of
+their access.
 """
 from = "now-9m"
 index = ["logs-endpoint.events.*"]

rules/_deprecated/execution_crash_binary.toml

@@ -1,7 +1,8 @@
 [metadata]
 creation_date = "2022/03/21"
-maturity = "production"
-updated_date = "2022/04/29"
+deprecation_date = "2022/05/09"
+maturity = "deprecated"
+updated_date = "2022/05/09"
 
 [rule]
 author = ["Elastic"]

rules/_deprecated/execution_env_binary.toml

@@ -1,7 +1,8 @@
 [metadata]
 creation_date = "2022/02/24"
-maturity = "production"
-updated_date = "2022/04/29"
+deprecation_date = "2022/05/09"
+maturity = "deprecated"
+updated_date = "2022/05/09"
 
 [rule]
 author = ["Elastic"]

rules/_deprecated/execution_expect_binary.toml

@@ -1,7 +1,8 @@
 [metadata]
 creation_date = "2022/03/07"
-maturity = "production"
-updated_date = "2022/04/29"
+deprecation_date = "2022/05/09"
+maturity = "deprecated"
+updated_date = "2022/05/09"
 
 [rule]
 author = ["Elastic"]

rules/_deprecated/execution_find_binary.toml

@@ -1,7 +1,8 @@
 [metadata]
 creation_date = "2022/02/28"
-maturity = "production"
-updated_date = "2022/04/29"
+deprecation_date = "2022/05/09"
+maturity = "deprecated"
+updated_date = "2022/05/09"
 
 [rule]
 author = ["Elastic"]

rules/_deprecated/execution_flock_binary.toml

@@ -1,7 +1,8 @@
 [metadata]
 creation_date = "2022/03/22"
-maturity = "production"
-updated_date = "2022/04/29"
+deprecation_date = "2022/05/09"
+maturity = "deprecated"
+updated_date = "2022/05/09"
 
 [rule]
 author = ["Elastic"]

rules/_deprecated/execution_gcc_binary.toml

@@ -1,7 +1,8 @@
 [metadata]
 creation_date = "2022/03/09"
-maturity = "production"
-updated_date = "2022/04/29"
+deprecation_date = "2022/05/09"
+maturity = "deprecated"
+updated_date = "2022/05/09"
 
 [rule]
 author = ["Elastic"]

rules/_deprecated/execution_mysql_binary.toml

@@ -1,7 +1,8 @@
 [metadata]
 creation_date = "2022/03/09"
-maturity = "production"
-updated_date = "2022/04/29"
+deprecation_date = "2022/05/09"
+maturity = "deprecated"
+updated_date = "2022/05/09"
 
 [rule]
 author = ["Elastic"]

rules/_deprecated/execution_ssh_binary.toml

@@ -1,7 +1,8 @@
 [metadata]
 creation_date = "2022/03/10"
-maturity = "production"
-updated_date = "2022/04/29"
+deprecation_date = "2022/05/09"
+maturity = "deprecated"
+updated_date = "2022/05/09"
 
 [rule]
 author = ["Elastic"]

rules/_deprecated/execution_vi_binary.toml

@@ -1,7 +1,8 @@
 [metadata]
 creation_date = "2022/03/03"
-maturity = "production"
-updated_date = "2022/04/29"
+deprecation_date = "2022/05/09"
+maturity = "deprecated"
+updated_date = "2022/05/09"
 
 [rule]
 author = ["Elastic"]

rules/linux/execution_nice_binary.toml

@@ -1,51 +0,0 @@
-[metadata]
-creation_date = "2022/03/07"
-maturity = "development"
-updated_date = "2022/03/31"
-
-[rule]
-author = ["Elastic"]
-description = """
-Identifies Linux binary nice abuse to break out from restricted environments by spawning an interactive system shell.The
-nice command is used to invoke a utility or a shell script with a particular CPU priority, thus giving the process more
-or less CPU and the activity of spawning shell is not a standard use of this binary for 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 nice Shell evasion"
-references = ["https://gtfobins.github.io/gtfobins/nice/"]
-risk_score = 47
-rule_id = "22755f7f-1e1e-4528-a75f-bb3f4026d1b9"
-severity = "medium"
-tags = ["Elastic", "Host", "Linux", "Threat Detection", "Execution", "GTFOBins"]
-timestamp_override = "event.ingested"
-type = "eql"
-
-query = '''
-process where event.type == "start" and process.name in ("bash", "sh", "dash") and
-  process.parent.name == "nice" and process.parent.args in ("/bin/bash", "/bin/sh", "/bin/dash", "sh", "bash", "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/"
-

rules/linux/execution_shell_evasion_linux_binary.toml

@@ -0,0 +1,103 @@
+[metadata]
+creation_date = "2022/05/06"
+maturity = "production"
+updated_date = "2022/05/09"
+
+[rule]
+author = ["Elastic"]
+description = """
+Identifies Linux binary(s) abuse to breakout out of restricted shells or environments by spawning an interactive system
+shell. The linux utility(s) activity of spawning shell is not a standard use of the binary for a user or system
+administrator. It may indicates an attempt to improve the capabilities or stability of an adversary access.
+"""
+from = "now-9m"
+index = ["logs-endpoint.events.*"]
+language = "eql"
+license = "Elastic License v2"
+name = "Linux Restricted Shell Breakout via  Linux Binary(s)"
+references = [
+    "https://gtfobins.github.io/gtfobins/apt/",
+    "https://gtfobins.github.io/gtfobins/apt-get/",
+    "https://gtfobins.github.io/gtfobins/nawk/",
+    "https://gtfobins.github.io/gtfobins/mawk/",
+    "https://gtfobins.github.io/gtfobins/awk/",
+    "https://gtfobins.github.io/gtfobins/gawk/",
+    "https://gtfobins.github.io/gtfobins/busybox/",
+    "https://gtfobins.github.io/gtfobins/c89/",
+    "https://gtfobins.github.io/gtfobins/c99/",
+    "https://gtfobins.github.io/gtfobins/cpulimit/",
+    "https://gtfobins.github.io/gtfobins/crash/",
+    "https://gtfobins.github.io/gtfobins/env/",
+    "https://gtfobins.github.io/gtfobins/expect/",
+    "https://gtfobins.github.io/gtfobins/find/",
+    "https://gtfobins.github.io/gtfobins/flock/",
+    "https://gtfobins.github.io/gtfobins/gcc/",
+    "https://gtfobins.github.io/gtfobins/mysql/",
+    "https://gtfobins.github.io/gtfobins/nice/",
+    "https://gtfobins.github.io/gtfobins/ssh/",
+    "https://gtfobins.github.io/gtfobins/vi/",
+    "https://gtfobins.github.io/gtfobins/vim/",
+    "https://gtfobins.github.io/gtfobins/capsh/",
+    "https://gtfobins.github.io/gtfobins/byebug/",
+]
+risk_score = 47
+rule_id = "52376a86-ee86-4967-97ae-1a05f55816f0"
+severity = "medium"
+tags = ["Elastic", "Host", "Linux", "Threat Detection", "Execution", "GTFOBins"]
+timestamp_override = "event.ingested"
+type = "eql"
+
+query = '''
+process where event.type == "start" and
+
+  /* launch shells from unusual process */
+  (process.name == "capsh" and process.args == "--") or
+
+  /* launching shells from unusual parents or parent+arg combos */
+  (process.name in ("bash", "sh", "dash","ash") and
+    (process.parent.name == "byebug") or
+
+    /* shells specified in parent args */
+    /* nice rule is broken in 8.2 */
+    (process.parent.args in ("/bin/sh", "/bin/bash", "/bin/dash", "/bin/ash", "sh", "bash", "dash", "ash") and
+        (process.parent.name == "nice") or
+        (process.parent.name == "cpulimit" and process.parent.args == "-f") or
+        (process.parent.name == "find" and process.parent.args == "-exec" and process.parent.args == ";") or
+        (process.parent.name == "flock" and process.parent.args == "-u" and process.parent.args == "/")
+    ) or
+
+    /* shells specified in args */
+    (process.args in ("/bin/sh", "/bin/bash", "/bin/dash", "/bin/ash", "sh", "bash", "dash", "ash") and
+        (process.parent.name == "crash" and process.parent.args == "-h") or
+        (process.name == "sensible-pager" and process.parent.name in ("apt", "apt-get") and process.parent.args == "changelog")
+        /* scope to include more sensible-pager invoked shells with different parent process to reduce noise and remove false positives */
+    )
+  ) or
+  (process.name == "busybox" and process.args_count == 2 and process.args in ("/bin/sh", "/bin/bash", "/bin/dash", "/bin/ash", "sh", "bash", "dash", "ash") )or
+  (process.name == "env" and process.args_count == 2 and process.args in ("/bin/sh", "/bin/bash", "/bin/dash", "/bin/ash", "sh", "bash", "dash", "ash")) or
+  (process.parent.name in ("vi", "vim") and process.parent.args == "-c" and process.parent.args in (":!/bin/bash", ":!/bin/sh", ":!bash", ":!sh")) or
+  (process.parent.name in ("c89","c99", "gcc") and process.parent.args in ("sh,-s", "bash,-s", "dash,-s", "ash,-s", "/bin/sh,-s", "/bin/bash,-s", "/bin/dash,-s", "/bin/ash,-s") and process.parent.args == "-wrapper") or
+  (process.parent.name == "expect" and process.parent.args == "-c" and process.parent.args in ("spawn /bin/sh;interact", "spawn /bin/bash;interact", "spawn /bin/dash;interact", "spawn sh;interact", "spawn bash;interact", "spawn dash;interact")) or
+  (process.parent.name == "mysql" and process.parent.args == "-e" and process.parent.args in ("\\!*sh", "\\!*bash", "\\!*dash", "\\!*/bin/sh", "\\!*/bin/bash", "\\!*/bin/dash")) or
+  (process.parent.name == "ssh" and process.parent.args == "-o" and process.parent.args in ("ProxyCommand=;sh 0<&2 1>&2", "ProxyCommand=;bash 0<&2 1>&2", "ProxyCommand=;dash 0<&2 1>&2", "ProxyCommand=;/bin/sh 0<&2 1>&2", "ProxyCommand=;/bin/bash 0<&2 1>&2", "ProxyCommand=;/bin/dash 0<&2 1>&2")) or
+  (process.parent.name in ("nawk", "mawk", "awk", "gawk") and process.parent.args : "BEGIN {system(*)}")
+'''
+
+
+[[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/"