# T1543 - Create or Modify System Process

## SOC Recommendation
Investigate Create or Modify System Process activity in the context of Persistence/Privilege Escalation: confirm scope, affected host/identity, and whether it matches expected administrative behaviour before deciding this is benign.

## D3FEND Mappings
| D3FEND Technique | Relationship | Practical SOC Action |
|---|---|---|
| File Analysis | Detect | Monitor for File Analysis indicators relevant to this technique. |
| File Encryption | Harden | Apply File Encryption to reduce this technique's viability before an incident occurs. |
| File Eviction | Evict | Use File Eviction to remove the adversary's foothold once this technique is confirmed. |
| Content Filtering | Isolate | Apply Content Filtering to contain the blast radius once this technique is observed. |

## Investigation Steps
1. Review Defender for Endpoint / Defender XDR alerts and timeline for the affected host or identity.
2. Check Sentinel analytics rules and incidents correlated with this technique.
3. Review Entra ID sign-in and audit logs if the technique involves an identity or cloud resource.

## Evidence to Collect
- Host or resource affected
- Account or identity involved
- Timestamp of the activity
- Related process, file, or network artifact
- Any preceding or follow-on alerts

## Response Actions
| Action | Risk | Automation Safe | Approval Required |
|---|---|---|---|
| Stop and delete the malicious service: sc stop <name> then | Low | No | Yes |
| Delete or quarantine the service binary | Low | No | Yes |
| If PsExec: investigate the origin host — it is the attacker' | Low | No | Yes |
| Check for additional services created in the same time windo | Low | Yes | No |

## KQL
```kql
DeviceEvents
| where ActionType has "ExploitGuardNonMicrosoftSignedBlocked"
| where InitiatingProcessFileName has "svchost.exe" and FileName has "NetSetupSvc.dll"
| extend HashAlgorithm = "SHA1"
| extend HostName = tostring(split(DeviceName, ".")[0]), DomainIndex = toint(indexof(DeviceName, '.'))
| extend HostNameDomain = iff(DomainIndex != -1, substring(DeviceName, DomainIndex + 1), DeviceName)
```
```kql
Pathlock_TDnR_CL
| where DataSource == "OS_CMD_CHANGES"
| project TimeGenerated, Sysid, DataSource, Eventid, Instance, Hostname, Bname,
          Tcode, Report, Area, Subid, SrcIp, DestIp, AffectedUser, LogLine,
          MsgType, MsgId, MsgNo, MessageV1, MessageV2, MessageV3, MessageV4, CentralTs
```
```kql
Pathlock_TDnR_CL
| where DataSource == "TRANSPORT_LOG"
| project TimeGenerated, Sysid, DataSource, Eventid, Instance, Hostname, Bname,
          Tcode, Report, Area, Subid, SrcIp, DestIp, AffectedUser, LogLine,
          MsgType, MsgId, MsgNo, MessageV1, MessageV2, MessageV3, MessageV4, CentralTs
```

## Escalation Criteria
- Create or Modify System Process activity observed on a privileged account or critical system.
- Activity follows or precedes other suspicious behaviour in the same investigation.
- Automated triage cannot confidently rule out malicious intent.

## False Positive Considerations
- Legitimate administrative or maintenance activity matching this pattern.
- Approved security testing or red team exercise.
- Known benign software producing similar telemetry.

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