Suspicious use of CPL file

Group by: SHA1
Author: FalconForce
Source: github.com/FalconForceTeam/FalconFriday

This query identifies .cpl files being loaded and verifies if the corresponding file is suspicious by looking at the signature and global prevalence.

Known false positives

Legitimate custom software might create a control panel item that is unsigned or has a low global prevalence.

MITRE ATT&CK coverage

Tactic	Techniques
Stealth	`T1218.002` System Binary Proxy Execution: Control Panel

References

Telemetry coverage

Platform	Record / event type
Microsoft Defender for Endpoint	`DeviceImageLoadEvents` action `ImageLoaded`: Image loaded
Microsoft Defender for Endpoint	`DeviceImageLoadEvents` action `any`: Image load

Rule body

let timeframe = 2*1h;
let default_global_prevalence = 0;
let suspiciousCPLs = DeviceImageLoadEvents
    | where ingestion_time() >= ago(timeframe)
    // Begin environment-specific filter.
    // End environment-specific filter.
    | where FileName endswith ".cpl"
    | summarize by SHA1
    // FileProfile is case-sensitive and works on lower-case hashes.
    | extend SHA1=tolower(SHA1)
    | invoke FileProfile(SHA1, 1000)
    | where not(ProfileAvailability =~ "Error")
    // Begin environment-specific filter.
    // End environment-specific filter.
    | where ((isempty(Signer) or not(IsCertificateValid==1)) and coalesce(GlobalPrevalence,default_global_prevalence) < 100) or coalesce(GlobalPrevalence,default_global_prevalence) < 50;
let loadedDlls=DeviceImageLoadEvents
    | where ingestion_time() >= ago(timeframe)
    // FileProfile is case-sensitive and works on lower-case hashes.
    | extend SHA1=tolower(SHA1)
    | where SHA1 in~ ((suspiciousCPLs|project SHA1)) and ActionType =~ "ImageLoaded"
    // Begin environment-specific filter.
    // End environment-specific filter.
    ;
loadedDlls
    | join kind=leftouter suspiciousCPLs on SHA1
    // Begin environment-specific filter.
    // End environment-specific filter.

Stages and Predicates

Parameters

let timeframe = 2*1h;
let default_global_prevalence = 0;

let loadedDlls is inlined into the numbered stages below.

Let binding: `suspiciousCPLs` used in Stages 1, 7

let suspiciousCPLs = DeviceImageLoadEvents
    | where ingestion_time() >= ago(timeframe)
    | where FileName endswith ".cpl"
    | summarize by SHA1
    | extend SHA1=tolower(SHA1)
    | invoke FileProfile(SHA1, 1000)
    | where not(ProfileAvailability =~ "Error")
    | where ((isempty(Signer) or not(IsCertificateValid==1)) and coalesce(GlobalPrevalence,default_global_prevalence) < 100) or coalesce(GlobalPrevalence,default_global_prevalence) < 50;

Stage 1: `source`

let suspiciousCPLs

Stage 2: `source`

let loadedDlls

Stage 3: `source`

DeviceImageLoadEvents

Stage 4: `where`

where ...

Stage 5: `extend`

extend SHA1

Stage 6: `where`

where ActionType =~ "ImageLoaded"

Stage 7: `join`

join kind=leftouter (suspiciousCPLs) on SHA1

Stage 8: `summarize` aggregation inside the `join` branch

summarize by SHA1

Exclusions

The rule actively suppresses these predicates.

Field	Kind	Excluded values	Search
`ProfileAvailability`	eq	`Error`	`excludes:ProfileAvailability` `field:"ProfileAvailability" value:"Error"`

Indicators

These rows show field, operator, and value matches.

Field	Kind	Values	Search
`ActionType`	eq	`ImageLoaded`	`field:"ActionType" kind:eq value:"ImageLoaded"`
`FileName`	ends_with	`.cpl`	`field:"file_name" kind:ends_with value:".cpl"`
`GlobalPrevalence`	lt	`100` transforms: `coalesce_default:0` `50` transforms: `coalesce_default:0`	`field:"GlobalPrevalence" kind:lt`
`Signer`	is_null	(no value, null check)	`field:"Signer" kind:is_null`

Output fields

These fields are emitted when the rule matches.

Field	Source
`SHA1`	`summarize`

Suspicious use of CPL file

Known false positives

MITRE ATT&CK coverage

References

Telemetry coverage

Rule body

Stages and Predicates

Parameters

Let binding: suspiciousCPLs used in Stages 1, 7

Stage 1: source

Stage 2: source

Stage 3: source

Stage 4: where

Stage 5: extend

Stage 6: where

Stage 7: join

Stage 8: summarize aggregation inside the join branch