pua_nimgrab_execution

rule pua_nimgrab_execution {

  meta:
    author = "frack113"
    description = "Detects the usage of nimgrab, a tool bundled with the Nim programming framework and used for downloading files."
    reference = "https://github.com/SigmaHQ/sigma/blob/master/rules/windows/process_creation/proc_creation_win_pua_nimgrab.yml"
    license = "https://github.com/SigmaHQ/Detection-Rule-License/blob/main/LICENSE.Detection.Rules.md"
    rule_name = "PUA - Nimgrab Execution"
    sigma_uuid = "74a12f18-505c-4114-8d0b-8448dd5485c6"
    sigma_status = "test"
    rule_id = "mr_70b5f0f8-6bd3-42ab-be2f-928084b09942"
    tactic = "TA0011"
    technique = "T1105"
    type = "Detection"
    data_source = "Sysmon"
    platform = "Windows"
    severity = "High"
    priority = "High"
    false_positives = "Legitimate use of Nim on a developer systems"

  events:
    $process.metadata.event_type = "PROCESS_LAUNCH"
    (
        re.regex($process.target.process.file.full_path, `\\nimgrab\.exe$`) nocase or
        (
            strings.contains(strings.to_upper($process.target.process.file.md5), "2DD44C3C29D667F5C0EF5F9D7C7FFB8B") or
            strings.contains(strings.to_upper($process.target.process.file.sha256), "F266609E91985F0FE3E31C5E8FAEEEC4FFA5E0322D8B6F15FE69F4C5165B9559") or
            strings.contains(strings.to_upper($process.target.process.file.pe_file.imphash), "C07FDDD21D123EA9B3A08EEF44AAAC45")
        )
    )
    $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
}