Detection rules › Kusto

Potential re-named sdelete usage (ASIM Version)

Severity
low
Time window
1h
Author
Microsoft Security Research
Source
github.com/Azure/Azure-Sentinel

This detection looks for command line parameters associated with the use of Sysinternals sdelete (https://docs.microsoft.com/sysinternals/downloads/sdelete) to delete multiple files on a host's C drive. A threat actor may re-name the tool to avoid detection and then use it for destructive attacks on a host. This detection uses the ASIM imProcess parser, this will need to be deployed before use - https://docs.microsoft.com/azure/sentinel/normalization

MITRE ATT&CK coverage

TacticTechniques
Stealth
Impact

Telemetry coverage

Rule body

id: 5b6ae038-f66e-4f74-9315-df52fd492be4
name: Potential re-named sdelete usage (ASIM Version)
description: |
  'This detection looks for command line parameters associated with the use of Sysinternals sdelete (https://docs.microsoft.com/sysinternals/downloads/sdelete) to delete multiple files on a host's C drive.
  A threat actor may re-name the tool to avoid detection and then use it for destructive attacks on a host.
  This detection uses the ASIM imProcess parser, this will need to be deployed before use - https://docs.microsoft.com/azure/sentinel/normalization'
severity: Low
requiredDataConnectors: []
queryFrequency: 1h
queryPeriod: 1h
triggerOperator: gt
triggerThreshold: 0
tactics:
  - DefenseEvasion
  - Impact
relevantTechniques:
  - T1485
  - T1036
query: |
  imProcess
  | where CommandLine has_all ("accepteula", "-s", "-r", "-q")
  | where Process !endswith "sdelete.exe"
  | where CommandLine !has "sdelete"
  | extend AccountName = tostring(split(ActorUsername, @'\')[1]), AccountNTDomain = tostring(split(ActorUsername, @'\')[0])
entityMappings:
  - entityType: Account
    fieldMappings:
      - identifier: FullName
        columnName: ActorUsername
      - identifier: Name
        columnName: AccountName
      - identifier: NTDomain
        columnName: AccountNTDomain
  - entityType: Host
    fieldMappings:
      - identifier: FullName
        columnName: Dvc
      - identifier: HostName
        columnName: DvcHostname
      - identifier: DnsDomain
        columnName: DvcDomain
  - entityType: IP
    fieldMappings:
      - identifier: Address
        columnName: DvcIpAddr
version: 1.0.6
kind: Scheduled
metadata:
    source:
        kind: Community
    author:
        name: Microsoft Security Research
    support:
        tier: Community
    categories:
        domains: [ "Security - Threat Protection" ]

Stages and Predicates

Stage 1: source

imProcess

Stage 2: where

| where CommandLine has_all ("accepteula", "-s", "-r", "-q")

Stage 3: where

| where Process !endswith "sdelete.exe"

Stage 4: where

| where CommandLine !has "sdelete"

Stage 5: extend

| extend AccountName = tostring(split(ActorUsername, @'\')[1]), AccountNTDomain = tostring(split(ActorUsername, @'\')[0])

Exclusions

The rule actively suppresses these predicates.

FieldKindExcluded valuesSearch
Processends_withsdelete.exeexcludes:Process field:"Process" value:"sdelete.exe"
CommandLinematchsdeleteexcludes:CommandLine field:"CommandLine" value:"sdelete"

Indicators

These rows show field, operator, and value matches.

FieldKindValuesSearch
CommandLinematch
  • -q transforms: term corpus 9 (sigma 6, kusto 2, splunk 1)
  • -r transforms: term corpus 13 (sigma 9, kusto 4)
  • -s transforms: term corpus 10 (sigma 4, kusto 4, elastic 1, splunk 1)
  • accepteula transforms: term corpus 7 (sigma 3, kusto 3, splunk 1)
field:"CommandLine" kind:match

Output fields

These fields are emitted when the rule matches.

FieldSource
AccountNTDomainextend
AccountNameextend