Suspicious Process Access via Direct System Call

Last updated 5 months ago on 2025-03-20
Created 4 years ago on 2021-10-11

About

Identifies suspicious process access events from an unknown memory region. Endpoint security solutions usually hook userland Windows APIs in order to decide if the code that is being executed is malicious or not. It's possible to bypass hooked functions by writing malicious functions that call syscalls directly.
Tags
Domain: EndpointOS: WindowsUse Case: Threat DetectionTactic: Defense EvasionTactic: ExecutionData Source: SysmonLanguage: eql
Severity
high
Risk Score
73
MITRE ATT&CK™

Defense Evasion (TA0005)(opens in a new tab or window)

Execution (TA0002)(opens in a new tab or window)

License
Elastic License v2(opens in a new tab or window)

Definition

Rule Type
Event Correlation Rule
Integration Pack
Prebuilt Security Detection Rules
Index Patterns
winlogbeat-*logs-windows.sysmon_operational-*
Related Integrations

windows(opens in a new tab or window)

Query
process where host.os.type == "windows" and event.code == "10" and
 length(winlog.event_data.CallTrace) > 0 and

 /* Sysmon CallTrace starting with unknown memory module instead of ntdll which host Windows NT Syscalls */
 not winlog.event_data.CallTrace :
            ("?:\\WINDOWS\\SYSTEM32\\ntdll.dll*",
             "?:\\WINDOWS\\SysWOW64\\ntdll.dll*",
             "?:\\Windows\\System32\\wow64cpu.dll*",
             "?:\\WINDOWS\\System32\\wow64win.dll*",
             "?:\\Windows\\System32\\win32u.dll*") and

 not winlog.event_data.TargetImage :
            ("?:\\Program Files (x86)\\Malwarebytes Anti-Exploit\\mbae-svc.exe",
             "?:\\Program Files\\Cisco\\AMP\\*\\sfc.exe",
             "?:\\Program Files (x86)\\Microsoft\\EdgeWebView\\Application\\*\\msedgewebview2.exe",
             "?:\\Program Files\\Adobe\\Acrobat DC\\Acrobat\\*\\AcroCEF.exe") and

 not (process.executable : ("?:\\Program Files\\Adobe\\Acrobat DC\\Acrobat\\Acrobat.exe",
                            "?:\\Program Files (x86)\\World of Warcraft\\_classic_\\WowClassic.exe") and
      not winlog.event_data.TargetImage : "?:\\WINDOWS\\system32\\lsass.exe")

Install detection rules in Elastic Security

Detect Suspicious Process Access via Direct System Call in the Elastic Security detection engine by installing this rule into your Elastic Stack.

To setup this rule, check out the installation guide for Prebuilt Security Detection Rules(opens in a new tab or window).