potential_tampering_with_rdp_related_registry_keys_via_reg_exe

rule potential_tampering_with_rdp_related_registry_keys_via_reg_exe {

  meta:
    author = "pH-T (Nextron Systems), @Kostastsale, TheDFIRReport"
    description = "Detects the execution of reg.exe for enabling/disabling the RDP service on the host by tampering with the CurrentControlSet\\Control\\Terminal Server values"
    reference = "https://github.com/SigmaHQ/sigma/blob/master/rules/windows/process_creation/proc_creation_win_reg_rdp_keys_tamper.yml"
    license = "https://github.com/SigmaHQ/Detection-Rule-License/blob/main/LICENSE.Detection.Rules.md"
    rule_name = "Potential Tampering With RDP Related Registry Keys Via Reg.EXE"
    sigma_uuid = "0d5675be-bc88-4172-86d3-1e96a4476536"
    sigma_status = "test"
    rule_id = "mr_60818065-6198-4650-ab78-306267b5f165"
    tactic = "TA0005"
    technique = "T1112"
    type = "Detection"
    data_source = "Windows Event Logs"
    platform = "Windows"
    severity = "High"
    priority = "High"
    false_positives = "Unknown"

  events:
    $process.metadata.event_type = "PROCESS_LAUNCH"
    (
        re.regex($process.target.process.file.full_path, `\\reg\.exe$`) nocase or
        $process.src.process.file.full_path = "reg.exe" nocase
    )
    (
        strings.contains(strings.to_lower($process.target.process.command_line), " add ") and
        strings.contains(strings.to_lower($process.target.process.command_line), "\\currentcontrolset\\control\\terminal server") and
        strings.contains(strings.to_upper($process.target.process.command_line), "REG_DWORD") and
        strings.contains(strings.to_lower($process.target.process.command_line), " /f")
    )
    (
        (
        strings.contains(strings.to_lower($process.target.process.command_line), "licensing core") and
        strings.contains(strings.to_lower($process.target.process.command_line), "enableconcurrentsessions")
        )
        or
        (
            strings.contains(strings.to_lower($process.target.process.command_line), "winstations\\rdp-tcp") or
            strings.contains(strings.to_lower($process.target.process.command_line), "maxinstancecount") or
            strings.contains(strings.to_lower($process.target.process.command_line), "fenablewinstation") or
            strings.contains(strings.to_lower($process.target.process.command_line), "tsuserenabled") or
            strings.contains(strings.to_lower($process.target.process.command_line), "tsenabled") or
            strings.contains(strings.to_lower($process.target.process.command_line), "tsapcompat") or
            strings.contains(strings.to_lower($process.target.process.command_line), "idlewinstationpoolcount") or
            strings.contains(strings.to_lower($process.target.process.command_line), "tsadvertise") or
            strings.contains(strings.to_lower($process.target.process.command_line), "allowtsconnections") or
            strings.contains(strings.to_lower($process.target.process.command_line), "fsinglesessionperuser") or
            strings.contains(strings.to_lower($process.target.process.command_line), "fdenytsconnections")
        )
    )
    $process.principal.hostname = $hostname

  match:
    $hostname over 5m

  outcome:
    //example usage of specifying test user and hostname to adjust risk score
    $risk_score = max(if($process.principal.user.userid = "user" and $process.principal.hostname = "hostname", 0, 15))
    $principal_process_pid = array_distinct($process.principal.process.pid)
    $principal_process_command_line = array_distinct($process.principal.process.command_line)
    $principal_process_file_sha256 = array_distinct($process.principal.process.file.sha256)
    $principal_process_file_full_path = array_distinct($process.principal.process.file.full_path)
    $principal_process_product_specfic_process_id = array_distinct($process.principal.process.product_specific_process_id)
    $principal_process_parent_process_product_specfic_process_id = array_distinct($process.principal.process.parent_process.product_specific_process_id)
    $target_process_pid = array_distinct($process.target.process.pid)
    $target_process_command_line = array_distinct($process.target.process.command_line)
    $target_process_file_sha256 = array_distinct($process.target.process.file.sha256)
    $target_process_file_full_path = array_distinct($process.target.process.file.full_path)
    $target_process_product_specfic_process_id = array_distinct($process.target.process.product_specific_process_id)
    $principal_user_userid = array_distinct($process.principal.user.userid)
    $log_type = array_distinct(strings.concat($process.metadata.log_type,"/",$process.metadata.product_event_type))

  condition:
    $process
}