Clearing of Shell History via Environment Variables

[rule]
description = """
This rule detects the clearing of the shell history via environment variables. Attackers may clear the shell history to
hide their activities from being tracked. By leveraging environment variables such as HISTSIZE, HISTFILESIZE,
HISTCONTROL, and HISTFILE, attackers can clear the shell history by setting them to 0, ignoring spaces, or redirecting
the history to /dev/null, effectively erasing the command history.
"""
id = "f66e8880-ecfc-414f-8c1e-6e5892fac7e9"
license = "Elastic License v2"
name = "Clearing of Shell History via Environment Variables"
os_list = ["linux"]
reference = ["https://www.rapid7.com/blog/post/tr-new-whitepaper-stealthy-bpfdoor-variants/"]
version = "1.0.1"

query = '''
process where event.type == "start" and event.action == "exec" and process.env_vars like~ (
  "HISTSIZE=0", "HISTFILESIZE=0", "HISTCONTROL=ignorespace", "HISTFILE=/dev/null"
)
'''

min_endpoint_version = "8.6.0"
optional_actions = []
[[actions]]
action = "kill_process"
field = "process.entity_id"
state = 0

[[actions]]
action = "kill_process"
field = "process.parent.entity_id"
state = 0

[[threat]]
framework = "MITRE ATT&CK"
[[threat.technique]]
id = "T1070"
name = "Indicator Removal"
reference = "https://attack.mitre.org/techniques/T1070/"
[[threat.technique.subtechnique]]
id = "T1070.003"
name = "Clear Command History"
reference = "https://attack.mitre.org/techniques/T1070/003/"



[threat.tactic]
id = "TA0005"
name = "Defense Evasion"
reference = "https://attack.mitre.org/tactics/TA0005/"

[internal]
min_endpoint_version = "8.6.0"