Suspicious MSC File Launched

Group by: FolderPath, MscFile
Author: FalconForce
Source: github.com/FalconForceTeam/FalconFriday

The query searches for suspicious MSC files that are launched on the system. The following types of suspicious files are detected: MSC files downloaded by web browsers, MSC files in the Downloads folder, MSC files extracted from ZIP files, and MSC files with Mark Of The Web (MOTW).

MITRE ATT&CK coverage

Tactic	Techniques
Initial Access	`T1566` Phishing
Stealth	`T1218.014` System Binary Proxy Execution: MMC

References

https://www.elastic.co/security-labs/grimresource

Event coverage

Provider	Event/ActionType	Title
Sysmon	Event ID 1	Process creation
Sysmon	Event ID 11	FileCreate
Security-Auditing	Event ID 4663	An attempt was made to access an object.
Security-Auditing	Event ID 4688	A new process has been created.
Defender-DeviceFileEvents	FileCreated	File created
Defender-DeviceFileEvents	FileRenamed	File renamed
Defender-DeviceProcessEvents	ProcessCreated	Process created

Rule body kusto

let timeframe = 2*1h;
let RegexValidateTempZipPath = @"((?i)[^=|\/]*?AppData\\Local\\Temp\\(7z.........\\|wz....\\|Temp\d{1,3}_\w+)\b[^( ;)|]*)";
let MscRenamedFromCrDownload=(
    DeviceFileEvents
    | where ingestion_time() >= ago(timeframe)
    | where ActionType == "FileRenamed"
    | where FileName endswith ".msc"
    | where PreviousFileName endswith ".crdownload"
    | extend SuspiciousReason="MSC file downloaded by web browser."
);
let MscWrittenByBrowser=(
    DeviceFileEvents
    | where ingestion_time() >= ago(timeframe)
    | where ActionType == "FileRenamed" or ActionType == "FileCreated"
    | where FileName endswith ".msc"
    | where InitiatingProcessFileName in~ ("chrome.exe", "msedge.exe", "brave.exe", "opera.exe", "vivaldi.exe", "iexplore.exe", "msedgewebview2.exe", "firefox.exe")
    | extend SuspiciousReason="MSC file downloaded by web browser."
);
let MscInDownloadsFolder=(
    DeviceFileEvents
    | where ingestion_time() >= ago(timeframe)
    | where ActionType == "FileRenamed" or ActionType == "FileCreated"
    | where FileName endswith ".msc"
    | where FolderPath contains @"\downloads\"
    | extend SuspiciousReason="MSC file downloaded by web browser."
);
let MscDecompressed=(
    DeviceFileEvents
    | where ingestion_time() >= ago(timeframe)
    | where ActionType == "FileRenamed" or ActionType == "FileCreated"
    | where FileName endswith ".msc"
    | where InitiatingProcessFileName in~ ("7zfm.exe", "7zg.exe", "7z.exe", "winzip64.exe", "winrar.exe", "winzip.exe")
    or FolderPath matches regex RegexValidateTempZipPath
    or FolderPath contains @".zip\"
    | extend SuspiciousReason="MSC file extracted from zip file."
);
let MscMOTW=(
    DeviceFileEvents
    | where ingestion_time() >= ago(timeframe)
    | where ActionType == "FileRenamed" or ActionType == "FileCreated"
    | where FileName endswith ".msc"
    | where isnotempty(FileOriginUrl)
    | extend SuspiciousReason="MSC file with Mark Of The Web (MOTW)."
);
let SuspiciousMscFiles=(
    union MscRenamedFromCrDownload, MscWrittenByBrowser, MscInDownloadsFolder, MscDecompressed, MscMOTW
    | distinct FolderPath=tolower(FolderPath), DeviceId, FileOriginUrl, MscSHA1=SHA1, SuspiciousReason, MscCreatedBy=InitiatingProcessFolderPath, MscCreatedByCommandLine=InitiatingProcessCommandLine
);
DeviceProcessEvents
| where ingestion_time() >= ago(timeframe)
| where ActionType == "ProcessCreated"
| where FileName =~ "mmc.exe"
| extend ParsedCommandLine=parse_command_line(ProcessCommandLine, "windows")
// Look for process creations of mmc.exe where the .msc file is on the command-line, indicating that the user clicked on the .msc file.
| where tostring(ParsedCommandLine) contains ".msc"
// When a .msc file is opened in MMC, the file path is passed as an argument to MMC.
// Based on testing this is the first argument in the command line. In some cases a command-line switch /32 is passed as the first argument
// and the file path is the second argument. This is handled by the iif statement below.
| extend MscFile=ParsedCommandLine[1]
| extend MscFile=iif(MscFile startswith "/", ParsedCommandLine[2], MscFile)
| extend MscFile=tolower(MscFile)
| lookup kind=inner SuspiciousMscFiles on DeviceId, $left.MscFile == $right.FolderPath
| project-reorder Timestamp, DeviceId, DeviceName, SuspiciousReason, MscFile,  MscCreatedBy, MscCreatedByCommandLine, MscSHA1
// Begin environment-specific filter.
// End environment-specific filter.

Stages and Predicates

Parameters

let timeframe = 2*1h;

Let binding: `RegexValidateTempZipPath`

let RegexValidateTempZipPath = @"((?i)[^=|\/]*?AppData\\Local\\Temp\\(7z.........\\|wz....\\|Temp\d{1,3}_\w+)\b[^( ;)|]*)";

Let binding: `MscRenamedFromCrDownload`

let MscRenamedFromCrDownload = (
    DeviceFileEvents
    | where ingestion_time() >= ago(timeframe)
    | where ActionType == "FileRenamed"
    | where FileName endswith ".msc"
    | where PreviousFileName endswith ".crdownload"
    | extend SuspiciousReason="MSC file downloaded by web browser."
);

Derived from timeframe.

Let binding: `MscWrittenByBrowser`

let MscWrittenByBrowser = (
    DeviceFileEvents
    | where ingestion_time() >= ago(timeframe)
    | where ActionType == "FileRenamed" or ActionType == "FileCreated"
    | where FileName endswith ".msc"
    | where InitiatingProcessFileName in~ ("chrome.exe", "msedge.exe", "brave.exe", "opera.exe", "vivaldi.exe", "iexplore.exe", "msedgewebview2.exe", "firefox.exe")
    | extend SuspiciousReason="MSC file downloaded by web browser."
);

Derived from timeframe.

Let binding: `MscInDownloadsFolder`

let MscInDownloadsFolder = (
    DeviceFileEvents
    | where ingestion_time() >= ago(timeframe)
    | where ActionType == "FileRenamed" or ActionType == "FileCreated"
    | where FileName endswith ".msc"
    | where FolderPath contains @"\downloads\"
    | extend SuspiciousReason="MSC file downloaded by web browser."
);

Derived from timeframe.

Let binding: `MscDecompressed`

let MscDecompressed = (
    DeviceFileEvents
    | where ingestion_time() >= ago(timeframe)
    | where ActionType == "FileRenamed" or ActionType == "FileCreated"
    | where FileName endswith ".msc"
    | where InitiatingProcessFileName in~ ("7zfm.exe", "7zg.exe", "7z.exe", "winzip64.exe", "winrar.exe", "winzip.exe")
    or FolderPath matches regex RegexValidateTempZipPath
    or FolderPath contains @".zip\"
    | extend SuspiciousReason="MSC file extracted from zip file."
);

Derived from timeframe, RegexValidateTempZipPath.

Let binding: `MscMOTW`

let MscMOTW = (
    DeviceFileEvents
    | where ingestion_time() >= ago(timeframe)
    | where ActionType == "FileRenamed" or ActionType == "FileCreated"
    | where FileName endswith ".msc"
    | where isnotempty(FileOriginUrl)
    | extend SuspiciousReason="MSC file with Mark Of The Web (MOTW)."
);

Derived from timeframe.

Let binding: `SuspiciousMscFiles`

let SuspiciousMscFiles = (
    union MscRenamedFromCrDownload, MscWrittenByBrowser, MscInDownloadsFolder, MscDecompressed, MscMOTW
    | distinct FolderPath=tolower(FolderPath), DeviceId, FileOriginUrl, MscSHA1=SHA1, SuspiciousReason, MscCreatedBy=InitiatingProcessFolderPath, MscCreatedByCommandLine=InitiatingProcessCommandLine
);

Derived from MscRenamedFromCrDownload, MscWrittenByBrowser, MscInDownloadsFolder, MscDecompressed, MscMOTW.

Stage 1: `source`

DeviceProcessEvents

Stage 2: `where`

| where ingestion_time() >= ago(timeframe)

Stage 3: `where`

| where ActionType == "ProcessCreated"

Stage 4: `where`

| where FileName =~ "mmc.exe"

Stage 5: `extend`

| extend ParsedCommandLine=parse_command_line(ProcessCommandLine, "windows")

Stage 6: `where`

| where tostring(ParsedCommandLine) contains ".msc"

Stage 7: `extend` (3 consecutive steps)

| extend MscFile=ParsedCommandLine[1]
| extend MscFile=iif(MscFile startswith "/", ParsedCommandLine[2], MscFile)
| extend MscFile=tolower(MscFile)

Stage 8: `kusto:lookup`

| lookup kind=inner SuspiciousMscFiles on DeviceId, $left.MscFile == $right.FolderPath

Stage 9: `project-reorder`

| project-reorder Timestamp, DeviceId, DeviceName, SuspiciousReason, MscFile,  MscCreatedBy, MscCreatedByCommandLine, MscSHA1

Indicators

Each row is a field, operator, and value that the rule matches. The corpus column counts how many other rules in the catalog look for the same combination: high numbers point to widely-used, community-vetted indicators. Blank or 1 shows that the indicator is specific to this rule.

Field	Kind	Values
`ActionType`	eq	`ProcessCreated` transforms: `cased` corpus 10 (kusto 10)
`FileName`	eq	`mmc.exe`
`ParsedCommandLine`	contains	`.msc` transforms: `tostring`

Output fields

Fields the rule emits when it matches. Chronicle authors list these in the outcome block; they appear on the detection and $risk_score drives alerting. Sentinel / Defender XDR rules build them up through project / summarize / extend stages. Sentinel maps these into alert fields via entityMappings and customDetails; Defender XDR custom detections surface them as alert fields directly.

Field	Source
`ParsedCommandLine`	`extend`
`MscFile`	`extend`

`j` / `k`	Scroll down / up
`d` / `u`	Half-page down / up
`gg` / `G`	Top / bottom
`h` / `l`	History back / forward
`f`	Follow link (`Shift` = new tab)
`/`	Focus search
`?`	Toggle this help
`↑` / `↓`	Navigate search results
`Enter`	Open highlighted result
`Esc`	Close results / dialog

`type:`	`events` / `rules` / `providers`
`vendor:`	`sigma` / `elastic` / `splunk` / `kusto` / `chronicle` (vendor name alone also works: `sigma:`, `kql:`, `secops:`…)
`tactic:`	TA-id, slug, or name: `credential_access`, `TA0006`
`technique:`	technique or sub-technique ID: `T1003`, `T1003.001` (alias `tech:`)
`severity:`	`critical` / `high` / `medium` / `low` / `informational` (alias `sev:`)
`risk_score`	Numeric comparison on the Elastic risk score (0 to 100): `risk_score>50`, `risk_score<=20`, `risk_score=99` (alias `risk`; Elastic rules only)
`stages:`	Rules with exactly N pipeline stages
`correlation:`	`single_event` / `sequence` / `alternatives` / `alternatives_cross_log` / `all_required` / `correlated`
`with:`	Co-occurrence event-id; stacks (`with:4624 with:4769`) to require all, while a comma list in one occurrence (`with:4624,4769`) is an either-or group. Implies multi-event
`like:`	Structural neighbors of a rule slug (equivalents + subsumption stricter / broader): `like:comsvcs_lsass_memory_dump-splunk-sysmon`
`groupby:`	Entity-grouping substring match against `group_by_keys`: `groupby:user`, `groupby:host`
`uses:`	Rules whose predicate tree touches the field (any kind, any value): `uses:CommandLine`
`excludes:`	Rules with top-level `not()` clauses on the field (FP whitelists): `excludes:ParentImage`
`field:` / `value:`	Predicate search; narrows rule cards to those with a matching leaf and drives the indicator tier. Unquoted = substring, wildcards allowed (`value:mimikatz`)
`indicator:`	Shorthand for `field:F value:V`: `indicator:Image=*\powershell.exe`
`kind:`	Filter by predicate kind. Narrows rule cards to those carrying a matching predicate leaf (`vendor:elastic kind:cidr_match`) and drives the indicator tier: `contains` / `starts_with` / `ends_with` / `regex` / `cidr` / `eq` / `in` … (operator aliases `op:`/`match:`)
`has:` / `no:`	`sample`, `field`, `notes`, `refs`, `trace`, `thirdparty`, `rule`, `pattern`, `timewindow`, `threshold`, `newterms`, `sigma`/`elastic`/`splunk`/`kusto`/`chronicle`
`-op:val`	Exclude matches; works on most operators but not `type:`/`like:`/`has:`/`no:` (use `no:<flag>` to exclude a rule flag): `tactic:execution -vendor:splunk`. Standalone `-kind:`/`-field:`/`-value:` drop every rule carrying a matching predicate leaf (`type:rules -kind:is_null`)
`field:"…"` / `value:"…"`	Quoted value = anchored exact match (also allows spaces): `value:"net user"`
`a,b`	Comma = OR inside one operator (`vendor:sigma,elastic`, `severity:high,critical`); repeating a facet merges the same way. `field:`/`value:` never split (literal commas)
`vendors:` / `stage:`	Singular and plural spellings fold to the canonical operator and value: `tactics:` = `tactic:`, `type:event` = `type:events`, `correlation:sequences` = `correlation:sequence`, `has:thresholds` = `has:threshold`
`"quoted phrase"`	Exact-match a multi-word phrase (free text)

Suspicious MSC File Launched

MITRE ATT&CK coverage

References

Event coverage

Rule body kusto

Stages and Predicates

Parameters

Let binding: `RegexValidateTempZipPath`

Let binding: `MscRenamedFromCrDownload`

Let binding: `MscWrittenByBrowser`

Let binding: `MscInDownloadsFolder`

Let binding: `MscDecompressed`

Let binding: `MscMOTW`

Let binding: `SuspiciousMscFiles`

Stage 1: `source`

Stage 2: `where`

Stage 3: `where`

Stage 4: `where`

Stage 5: `extend`

Stage 6: `where`

Stage 7: `extend` (3 consecutive steps)

Stage 8: `kusto:lookup`

Stage 9: `project-reorder`

Indicators

Output fields

Keyboard shortcuts

Search operators

Suspicious MSC File Launched

MITRE ATT&CK coverage

References

Event coverage

Rule body kusto

Stages and Predicates

Parameters

Let binding: RegexValidateTempZipPath

Let binding: MscRenamedFromCrDownload

Let binding: MscWrittenByBrowser

Let binding: MscInDownloadsFolder

Let binding: MscDecompressed

Let binding: MscMOTW

Let binding: SuspiciousMscFiles

Stage 1: source

Stage 2: where

Stage 3: where

Stage 4: where

Stage 5: extend

Stage 6: where

Stage 7: extend (3 consecutive steps)

Stage 8: kusto:lookup

Stage 9: project-reorder

Indicators

Output fields

Let binding: `RegexValidateTempZipPath`

Let binding: `MscRenamedFromCrDownload`

Let binding: `MscWrittenByBrowser`

Let binding: `MscInDownloadsFolder`

Let binding: `MscDecompressed`

Let binding: `MscMOTW`

Let binding: `SuspiciousMscFiles`

Stage 1: `source`

Stage 2: `where`

Stage 3: `where`

Stage 4: `where`

Stage 5: `extend`

Stage 6: `where`

Stage 7: `extend` (3 consecutive steps)

Stage 8: `kusto:lookup`

Stage 9: `project-reorder`