Input Injection

let SuspiciousChildProcs = dynamic(["powershell.exe", "cmd.exe", "wscript.exe", "cscript.exe", "mshta.exe", "rundll32.exe", "regsvr32.exe", "certutil.exe"]);
let EncodedFlags = dynamic(["-EncodedCommand", "-enc ", "-e ", "IEX", "Invoke-Expression", "DownloadString", "DownloadFile", "FromBase64String", "-WindowStyle Hidden", "-NoProfile", "-NonInteractive"]);
// Detect shell processes spawned via simulated input from desktop/shell parents with obfuscated command lines
let HIDSpawnedShells = DeviceProcessEvents
| where TimeGenerated > ago(1d)
| where InitiatingProcessFileName in~ ("explorer.exe", "winlogon.exe", "userinit.exe", "sihost.exe", "taskhostw.exe")
| where FileName in~ (SuspiciousChildProcs)
| where ProcessCommandLine has_any (EncodedFlags)
| project TimeGenerated, DeviceName, AccountName, InitiatingProcessFileName, InitiatingProcessId,
    FileName, ProcessId, ProcessCommandLine, InitiatingProcessCommandLine,
    FolderPath, SHA256, ReportId;
// Detect browser developer console or address bar manipulation patterns (BackSwap-style)
let BrowserInjection = DeviceProcessEvents
| where TimeGenerated > ago(1d)
| where InitiatingProcessFileName in~ ("chrome.exe", "firefox.exe", "msedge.exe", "iexplore.exe", "brave.exe")
| where FileName in~ ("powershell.exe", "cmd.exe", "wscript.exe", "cscript.exe")
| project TimeGenerated, DeviceName, AccountName, InitiatingProcessFileName, InitiatingProcessId,
    FileName, ProcessId, ProcessCommandLine, FolderPath, SHA256, ReportId;
// Union both patterns
union HIDSpawnedShells, BrowserInjection
| extend InjectionType = iff(InitiatingProcessFileName in~ ("chrome.exe", "firefox.exe", "msedge.exe", "iexplore.exe", "brave.exe"), "BrowserInputInjection", "HIDKeystrokeInjection")
| order by TimeGenerated desc
| project TimeGenerated, DeviceName, AccountName, InjectionType, InitiatingProcessFileName,
    InitiatingProcessId, FileName, ProcessId, ProcessCommandLine, SHA256, ReportId

index=* sourcetype="XmlWinEventLog:Microsoft-Windows-Sysmon/Operational" EventCode=1
| eval ParentImage=lower(ParentImage), Image=lower(Image), CommandLine=lower(CommandLine)
| where (match(ParentImage, "(explorer\.exe|winlogon\.exe|userinit\.exe|sihost\.exe|taskhostw\.exe)$")
    AND match(Image, "(powershell\.exe|cmd\.exe|wscript\.exe|cscript\.exe|mshta\.exe|rundll32\.exe|regsvr32\.exe|certutil\.exe)$")
    AND (match(CommandLine, "(-encodedcommand|-enc |-e |iex|invoke-expression|downloadstring|downloadfile|frombase64string|-windowstyle hidden|-noprofile|-noninteractive)")))
    OR (match(ParentImage, "(chrome\.exe|firefox\.exe|msedge\.exe|iexplore\.exe|brave\.exe)$")
    AND match(Image, "(powershell\.exe|cmd\.exe|wscript\.exe|cscript\.exe)$"))
| eval InjectionType=case(
    match(ParentImage, "(chrome\.exe|firefox\.exe|msedge\.exe|iexplore\.exe|brave\.exe)$"), "BrowserInputInjection",
    match(ParentImage, "(explorer\.exe|winlogon\.exe|userinit\.exe|sihost\.exe|taskhostw\.exe)$"), "HIDKeystrokeInjection",
    true(), "Unknown")
| table _time, host, User, InjectionType, ParentImage, ParentProcessId, Image, ProcessId, CommandLine, Hashes
| sort -_time

process where event.type == "start" and (
  process.name in~ ("powershell.exe", "cmd.exe", "wscript.exe", "cscript.exe") or
  process.parent.name in~ ("cmd.exe", "powershell.exe", "wscript.exe")
) and (
  process.command_line : ("*t1674*", "*suspicious*") or
  process.args : ("*encoded*", "*bypass*", "*hidden*")
) and not process.code_signature.trusted == true

SELECT
    DATEFORMAT(devicetime, 'yyyy-MM-dd HH:mm:ss') AS EventTime,
    LOGSOURCENAME(logsourceid) AS LogSource,
    "username" AS AccountName,
    "CommandLine" AS CommandLine,
    "ParentProcessName" AS ParentProcess,
    "NewProcessName" AS ProcessName,
    CASE
        WHEN "CommandLine" ILIKE '%powershell%' AND "CommandLine" ILIKE '%-enc%' THEN 'EncodedCommand'
        WHEN "CommandLine" ILIKE '%bypass%' THEN 'ExecutionBypass'
        WHEN "CommandLine" ILIKE '%-noprofile%' THEN 'NoProfileExecution'
        ELSE 'SuspiciousProcess'
    END AS DetectionType,
    CASE
        WHEN "username" = 'SYSTEM' THEN 70
        WHEN "CommandLine" ILIKE '%bypass%' THEN 85
        ELSE 60
    END AS RiskScore
FROM events
WHERE
    LOGSOURCETYPENAME(devicetype) IN ('Microsoft Windows Security Event Log', 'Universal DSM')
    AND eventid IN (4688, 1)
    AND ("NewProcessName" ILIKE '%powershell.exe%'
        OR "NewProcessName" ILIKE '%cmd.exe%'
        OR "NewProcessName" ILIKE '%wscript.exe%'
        OR "NewProcessName" ILIKE '%cscript.exe%'
        OR "NewProcessName" ILIKE '%mshta.exe%')
    AND RiskScore >= 60
ORDER BY EventTime DESC
LAST 1 HOURS

_sourceCategory=windows/sysmon EventCode=1
| json auto
| where process_name in ("powershell.exe", "cmd.exe", "wscript.exe", "cscript.exe", "mshta.exe", "rundll32.exe")
| where process_cmdline matches /(-enc|-encodedcommand|-bypass|-hidden|invoke-expression|iex\s)/i
    OR process_cmdline matches /(http:\/\/|https:\/\/|ftp:\/\/)/i
| if(process_cmdline matches /-enc/i, "EncodedCommand",
    if(process_cmdline matches /-bypass/i, "BypassExecution",
    if(process_cmdline matches /(invoke-expression|iex)/i, "ScriptExecution",
    "SuspiciousProcess"))) as detection_type
| if(parent_process_name in ("w3wp.exe","httpd.exe","nginx.exe"), 95,
    if(process_cmdline matches /-enc/i, 85,
    if(process_cmdline matches /-bypass/i, 75, 60))) as risk_score
| where risk_score >= 60
| count by host, user, process_name, process_cmdline, parent_process_name, detection_type, risk_score
| sort - risk_score

rule detection_t1674 {
  meta:
    author = "Argus Detection Platform"
    description = "Detects Input Injection - T1674"
    severity = "HIGH"
    mitre_attack = "T1674"
    reference = "https://attack.mitre.org/techniques/T1674/"

  events:
    $e.metadata.event_type = "PROCESS_LAUNCH"
    $e.principal.hostname = $hostname
    $e.target.process.file.full_path = $process_path
    $e.target.process.command_line = $cmdline
    (
      re.regex($e.target.process.file.full_path, `(?i)(powershell|cmd|wscript|cscript|mshta|rundll32)\.exe$`) and
      (
        re.regex($e.target.process.command_line, `(?i)-enc(odedcommand)?`) or
        re.regex($e.target.process.command_line, `(?i)-bypass`) or
        re.regex($e.target.process.command_line, `(?i)(invoke-expression|iex\s)`) or
        re.regex($e.target.process.command_line, `(?i)http://`)
      )
    )
    not re.regex($e.principal.process.file.full_path, `(?i)(trustedinstaller|msiexec|svchost)`)

  condition:
    $e
}

#event_simpleName = "ProcessRollup2"
| ImageFileName = /(?i)(powershell|cmd|wscript|cscript|mshta|rundll32)\.exe$/
| CommandLine = /(?i)(-enc(odedcommand)?|-bypass|-noprofile|invoke-expression|iex\s|http:\/\/)/
| case {
    CommandLine = /(?i)-enc(odedcommand)?/ | DetectionType := "EncodedCommand" ;
    CommandLine = /(?i)-bypass/ | DetectionType := "BypassExecution" ;
    CommandLine = /(?i)(invoke-expression|iex\s)/ | DetectionType := "ScriptExecution" ;
    * | DetectionType := "SuspiciousProcess"
}
| case {
    ParentBaseFileName = /(?i)(w3wp|httpd|nginx|php-cgi)\.exe/ | RiskScore := "Critical" ;
    CommandLine = /(?i)-enc/ | RiskScore := "High" ;
    * | RiskScore := "Medium"
}
| table([ComputerName, UserName, ImageFileName, CommandLine, ParentBaseFileName, DetectionType, RiskScore, ProcessId, ParentProcessId])
| sort(RiskScore, order=desc, limit=100)