Persistence Via Scheduled Tasks

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

This query identifies binaries that run as a scheduled task, by looking at the parent process command line. Of the identified binaries running as scheduled tasks it finds suspicious binaries by looking at the file signature and global prevalence.

MITRE ATT&CK coverage

Tactic	Techniques
Execution	`T1053.005` Scheduled Task/Job: Scheduled Task
Persistence	`T1053.005` Scheduled Task/Job: Scheduled Task
Privilege Escalation	`T1053.005` Scheduled Task/Job: Scheduled Task

References

https://medium.com/falconforce/malicious-scheduled-tasks-debc64633f81

Event coverage

Provider	Event/ActionType	Title
Sysmon	Event ID 1	Process creation
Security-Auditing	Event ID 4688	A new process has been created.
Defender-DeviceProcessEvents	ProcessCreated	Process created

Rule body kusto

let timeframe = 2*1d;
let default_global_prevalence = 0;
// Time to look back for same scheduled binary.
let lookback= 7d;
let ScheduledBinaries = (
    DeviceProcessEvents
    | where Timestamp >= ago(lookback)
    | where ActionType =~ "ProcessCreated"
    | where InitiatingProcessCommandLine startswith "svchost.exe -k netsvcs -p" and InitiatingProcessCommandLine contains "Schedule" // First argument after -p is censored with ** so can't look for the actual command line
);
let NewScheduledBinaries=(
    ScheduledBinaries
    | where Timestamp >= ago(lookback)
    | summarize FirstSeen=min(Timestamp),LastSeen=max(Timestamp) by DeviceId, SHA1
    | where LastSeen >= ago(timeframe)
    | where FirstSeen >= ago(timeframe)
);
let NewScheduledBinaryExecution=(
    ScheduledBinaries
    | where ingestion_time() >= ago(timeframe)
    | lookup kind=inner NewScheduledBinaries on DeviceId, SHA1
);
NewScheduledBinaryExecution
| summarize MachineCount=dcount(DeviceId) by SHA1
// Find the max 1000 least used binaries.
| top 1000 by MachineCount asc
// FileProfile is case-sensitive and works on lower-case hashes.
| extend SHA1=tolower(SHA1)
| invoke FileProfile(SHA1,1000)
| where not(ProfileAvailability =~ "Error")
| where coalesce(GlobalPrevalence,default_global_prevalence) < 100
| join NewScheduledBinaryExecution on SHA1
| summarize arg_max(Timestamp, *), Devices=make_set(DeviceName), MachineCount=dcount(DeviceName) by SHA1 // Gives the last execution with all details per SHA1.
// Begin environment-specific filter.
// End environment-specific filter.

Stages and Predicates

Parameters

let timeframe = 2*1d;
let default_global_prevalence = 0;
let lookback = 7d;

Let binding: `NewScheduledBinaries`

let NewScheduledBinaries = (
    ScheduledBinaries
    | where Timestamp >= ago(lookback)
    | summarize FirstSeen=min(Timestamp),LastSeen=max(Timestamp) by DeviceId, SHA1
    | where LastSeen >= ago(timeframe)
    | where FirstSeen >= ago(timeframe)
);

Derived from timeframe, lookback, ScheduledBinaries.

The stages below define let NewScheduledBinaryExecution (the rule's main pipeline source).

Stage 1: `source`

DeviceProcessEvents

Stage 2: `where`

| where Timestamp >= ago(lookback)

Stage 3: `where`

| where ActionType =~ "ProcessCreated"

Stage 4: `where`

| where InitiatingProcessCommandLine startswith "svchost.exe -k netsvcs -p" and InitiatingProcessCommandLine contains "Schedule"

Stage 5: `where`

| where ingestion_time() >= ago(timeframe)

Stage 6: `kusto:lookup`

| lookup kind=inner NewScheduledBinaries on DeviceId, SHA1

The stages below run on NewScheduledBinaryExecution (the outer pipeline).

Stage 7: `summarize`

NewScheduledBinaryExecution
| summarize MachineCount=dcount(DeviceId) by SHA1

Stage 8: `top`

| top 1000 by MachineCount asc

Stage 9: `extend`

| extend SHA1=tolower(SHA1)

Stage 10: `invoke`

| invoke FileProfile(SHA1,1000)

Stage 11: `where`

| where not(ProfileAvailability =~ "Error")

Stage 12: `where`

| where coalesce(GlobalPrevalence,default_global_prevalence) < 100

Stage 13: `join`

| join NewScheduledBinaryExecution on SHA1

Stage 14: `summarize`

| summarize arg_max(Timestamp, *), Devices=make_set(DeviceName), MachineCount=dcount(DeviceName) by SHA1

Exclusions

Top-level NOT(...) conjuncts: predicates this rule actively suppresses.

Field	Kind	Excluded values
`ProfileAvailability`	eq	`Error`

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` corpus 10 (kusto 10)
`GlobalPrevalence`	lt	`100` transforms: `coalesce_default:0` corpus 4 (kusto 4)
`InitiatingProcessCommandLine`	contains	`Schedule` corpus 2 (splunk 1, kusto 1)
`InitiatingProcessCommandLine`	starts_with	`svchost.exe -k netsvcs -p`

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
`Devices`	`summarize`
`MachineCount`	`summarize`
`SHA1`	`summarize`

`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)

Persistence Via Scheduled Tasks

MITRE ATT&CK coverage

References

Event coverage

Rule body kusto

Stages and Predicates

Parameters

Let binding: `NewScheduledBinaries`

Stage 1: `source`

Stage 2: `where`

Stage 3: `where`

Stage 4: `where`

Stage 5: `where`

Stage 6: `kusto:lookup`

Stage 7: `summarize`

Stage 8: `top`

Stage 9: `extend`

Stage 10: `invoke`

Stage 11: `where`

Stage 12: `where`

Stage 13: `join`

Stage 14: `summarize`

Exclusions

Indicators

Output fields

Keyboard shortcuts

Search operators

Persistence Via Scheduled Tasks

MITRE ATT&CK coverage

References

Event coverage

Rule body kusto

Stages and Predicates

Parameters

Let binding: NewScheduledBinaries

Stage 1: source

Stage 2: where

Stage 3: where

Stage 4: where

Stage 5: where

Stage 6: kusto:lookup

Stage 7: summarize

Stage 8: top

Stage 9: extend

Stage 10: invoke

Stage 11: where

Stage 12: where

Stage 13: join

Stage 14: summarize

Exclusions

Indicators

Output fields

Let binding: `NewScheduledBinaries`

Stage 1: `source`

Stage 2: `where`

Stage 3: `where`

Stage 4: `where`

Stage 5: `where`

Stage 6: `kusto:lookup`

Stage 7: `summarize`

Stage 8: `top`

Stage 9: `extend`

Stage 10: `invoke`

Stage 11: `where`

Stage 12: `where`

Stage 13: `join`

Stage 14: `summarize`