Shell Spawned by Web Server - Windows (Windows Event Log)

Group by: _time, host, process_name
Source: github.com/anvilogic-forge/armory

This use case detects web server processes with child processes which can be an indication of a web shell attack

MITRE ATT&CK coverage

Tactic	Techniques
Persistence	`T1505.003` Server Software Component: Web Shell, `T1505.004` Server Software Component: IIS Components
Stealth	`T1218` System Binary Proxy Execution

References

Event coverage

Provider	Event	Title
Security-Auditing	Event ID 4688	A new process has been created.

Rule body yaml

id: '18748.32126'
title: Shell Spawned by Web Server - Windows
description: 'This use case detects web server processes with child processes which
  can be an indication of a web shell attack. - Threat Actor Association: Alloy Taurus/Gallium,
  OilRig, Volt Typhoon (Bronze Silhouette, Vanguard Panda) -- Software Association:
  ALPHV/BlackCat, Clop'
logic_format: Splunk
logic: '`get_endpoint_data` `get_endpoint_data_winevent` (TERM(EventCode=4688) OR
  "<EventID>4688<" OR Type=Process) (TERM(w3wp) OR TERM(httpd) OR TERM(nginx) OR TERM(php-cgi)
  OR TERM(tomcat) OR TERM(UMWorkerProcess)) (TERM(cmd) OR TERM(powershell) OR TERM(pwsh)
  OR TERM(csc) OR TERM(sh) OR TERM(bash) OR TERM(bitsadmin))| regex Creator_Process_Name="(?i)(w3wp|httpd|nginx|php-cgi|tomcat|UMWorkerProcess)\.exe"|
  regex New_Process_Name="(?i)(cmd|powershell|pwsh|csc|sh|bash|bitsadmin)\.exe" |
  table _time, host, user, signature_id, process, process_*, parent_process_* | bin
  span=1s | stats values(*) as * by _time, host, process_name | eventstats c(process_name)
  as c_process_name by process_name| where c_process_name < 25 '
techniques:
- persistence:server software component:iis components
- persistence:server software component:web shell
- defense-evasion:system binary proxy execution
technique_id:
- T1505.004
- T1505.003
- T1218
data_category:
- Windows event logs
references:
- https://www.microsoft.com/security/blog/2021/02/11/web-shell-attacks-continue-to-rise/
- https://www.huntress.com/blog/moveit-transfer-critical-vulnerability-rapid-response

Stages and Predicates

Stage 1: `search`

`get_endpoint_data` `get_endpoint_data_winevent` (TERM(EventCode=4688) OR "<EventID>4688<" OR Type=Process) (TERM(w3wp) OR TERM(httpd) OR TERM(nginx) OR TERM(php-cgi) OR TERM(tomcat) OR TERM(UMWorkerProcess)) (TERM(cmd) OR TERM(powershell) OR TERM(pwsh) OR TERM(csc) OR TERM(sh) OR TERM(bash) OR TERM(bitsadmin))

Stage 2: `regex`

| regex Creator_Process_Name="(?i)(w3wp|httpd|nginx|php-cgi|tomcat|UMWorkerProcess)\.exe"

Stage 3: `regex`

| regex New_Process_Name="(?i)(cmd|powershell|pwsh|csc|sh|bash|bitsadmin)\.exe"

Stage 4: `table`

| table _time, host, user, signature_id, process, process_*, parent_process_*

Stage 5: `bucket`

| bin span=1s

Stage 6: `stats`

| stats values(*) as * by _time, host, process_name

Stage 7: `eventstats`

| eventstats c(process_name) as c_process_name by process_name

Stage 8: `where`

| where c_process_name < 25

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
`Creator_Process_Name`	regex_match	`"(?i)(w3wp\|httpd\|nginx\|php-cgi\|tomcat\|UMWorkerProcess).exe"`
`EventCode`	eq	`4688` corpus 313 (splunk 283, kusto 30)
`New_Process_Name`	regex_match	`"(?i)(cmd\|powershell\|pwsh\|csc\|sh\|bash\|bitsadmin).exe"`
`c_process_name`	lt	`25` corpus 2 (splunk 2)

Search terms

Bare-string tokens in the SPL search body. Splunk matches each token against _raw (the untyped raw event text) anywhere it appears, not against a specific field. These don't surface in the Indicators table because they aren't predicates on a known field.

Stage	Term
1	`TERM`
1	`"<EventID>4688<"`
1	`TERM`
1	`w3wp`
1	`TERM`
1	`httpd`
1	`TERM`
1	`nginx`
1	`"php-cgi"`
1	`TERM`
1	`tomcat`
1	`TERM`
1	`UMWorkerProcess`
1	`TERM`
1	`cmd`
1	`TERM`
1	`powershell`
1	`TERM`
1	`pwsh`
1	`TERM`
1	`csc`
1	`TERM`
1	`sh`
1	`TERM`
1	`bash`
1	`TERM`
1	`bitsadmin`

`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)

Shell Spawned by Web Server - Windows (Windows Event Log)

MITRE ATT&CK coverage

References

Event coverage

Rule body yaml

Stages and Predicates

Stage 1: `search`

Stage 2: `regex`

Stage 3: `regex`

Stage 4: `table`

Stage 5: `bucket`

Stage 6: `stats`

Stage 7: `eventstats`

Stage 8: `where`

Indicators

Search terms

Keyboard shortcuts

Search operators

Shell Spawned by Web Server - Windows (Windows Event Log)

MITRE ATT&CK coverage

References

Event coverage

Rule body yaml

Stages and Predicates

Stage 1: search

Stage 2: regex

Stage 3: regex

Stage 4: table

Stage 5: bucket

Stage 6: stats

Stage 7: eventstats

Stage 8: where

Indicators

Search terms

Stage 1: `search`

Stage 2: `regex`

Stage 3: `regex`

Stage 4: `table`

Stage 5: `bucket`

Stage 6: `stats`

Stage 7: `eventstats`

Stage 8: `where`