Identify SysAid Server web shell creation

Severity: high
Time window: 5m
Group by: Account, CommandLine, Computer, ObjectName, ParentProcessName, Process, ProcessName, SubjectLogonId, TimeGenerated, timekey
Author: Microsoft Security Research
Source: github.com/Azure/Azure-Sentinel

This query looks for potential webshell creation by the threat actor Mercury after the sucessful exploitation of SysAid server. Reference: https://www.microsoft.com/security/blog/2022/08/25/mercury-leveraging-log4j-2-vulnerabilities-in-unpatched-systems-to-target-israeli-organizations/

MITRE ATT&CK coverage

Tactic	Techniques
Initial Access	`T1190` Exploit Public-Facing Application

Event coverage

Provider	Event	Title
Security-Auditing	Event ID 4663	An attempt was made to access an object.
Security-Auditing	Event ID 4688	A new process has been created.

Rule body kusto

id: 50eb4cbd-188f-44f4-b964-bab84dcdec10
name: Identify SysAid Server web shell creation 
description: |
  'This query looks for potential webshell creation by the threat actor Mercury after the sucessful exploitation of SysAid server. 
  Reference:  https://www.microsoft.com/security/blog/2022/08/25/mercury-leveraging-log4j-2-vulnerabilities-in-unpatched-systems-to-target-israeli-organizations/'
severity: High
requiredDataConnectors:
  - connectorId: SecurityEvents
    dataTypes:
      - SecurityEvent 
  - connectorId: WindowsSecurityEvents
    dataTypes:
      - SecurityEvent 
  - connectorId: MicrosoftThreatProtection
    dataTypes:
      - DeviceFileEvents
queryFrequency: 1d
queryPeriod: 1d
triggerOperator: gt
triggerThreshold: 0
tactics:
  - InitialAccess
relevantTechniques:
  - T1190
tags:
  - Mercury
  - Schema: ASIMFileEvent
    SchemaVersion: 0.1.0
query: |
  let timeframe = 1d;
  let time_window = 5m;
  (union isfuzzy=true
  (SecurityEvent
  | where TimeGenerated > ago(timeframe)
  | where EventID == 4688
  | where Process has_any ("java.exe", "javaw.exe") and CommandLine has "SysAidServer" 
  | summarize by ParentProcessName,Process, Account, Computer, CommandLine, timekey= bin(TimeGenerated, time_window), TimeGenerated, SubjectLogonId
  | join kind=inner(
  SecurityEvent
  | where TimeGenerated > ago(timeframe)
  | where EventID == 4663
  | where Process has_any ("java.exe", "javaw.exe")
  | where AccessMask in ('0x2','0x100', '0x10', '0x4')
  | where ObjectName endswith ".jsp" 
  | summarize by ParentProcessName, Account, Computer, ObjectName, ProcessName, timekey= bin(TimeGenerated, time_window), TimeGenerated, SubjectLogonId)
   on timekey, Computer, SubjectLogonId
  ),
  (DeviceFileEvents 
  | where InitiatingProcessFileName has_any ("java.exe", "javaw.exe")  
  | where InitiatingProcessCommandLine has "SysAidServer"  
  | where FileName endswith ".jsp" 
  | extend Account = strcat(InitiatingProcessAccountDomain, @'\', InitiatingProcessAccountName), Computer = DeviceName
  ),
  (imFileEvent
  | where TimeGenerated > ago(timeframe)
  | where EventType == "FileCreated"
  | where ActingProcessName has_any ("java.exe", "javaw.exe") 
  | where ActingProcessCommandLine has "SysAidServer"  
  | where FilePath endswith ".jsp" 
  | extend Account = ActorUsername, Computer = DvcHostname
  )
  )
  | extend AccountName = tostring(split(Account, @'\')[1]), AccountNTDomain = tostring(split(Account, @'\')[0])
  | extend HostName = tostring(split(Computer, ".")[0]), DomainIndex = toint(indexof(Computer, '.'))
  | extend HostNameDomain = iff(DomainIndex != -1, substring(Computer, DomainIndex + 1), Computer)
entityMappings:
  - entityType: Account
    fieldMappings:
      - identifier: FullName
        columnName: Account
      - identifier: Name
        columnName: AccountName
      - identifier: NTDomain
        columnName: AccountNTDomain
  - entityType: Host
    fieldMappings:
      - identifier: FullName
        columnName: Computer
      - identifier: HostName
        columnName: HostName
      - identifier: DnsDomain
        columnName: HostNameDomain
version: 1.0.3
kind: Scheduled
metadata:
    source:
        kind: Scheduled
    author:
        name: Microsoft Security Research
    support:
        tier: Community
    categories:
        domains: [ "Security - Others" ]

Stages and Predicates

Parameters

let timeframe = 1d;
let time_window = 5m;

union `isfuzzy=true` (3 sources)

Each leg below queries one source; the rule matches if any leg does. Sources: SecurityEvent, DeviceFileEvents, imFileEvent

Leg 1: `SecurityEvent`

SecurityEvent
| where TimeGenerated > ago(timeframe)
| where EventID == 4688
| where Process has_any ("java.exe", "javaw.exe") and CommandLine has "SysAidServer" 
| summarize by ParentProcessName,Process, Account, Computer, CommandLine, timekey= bin(TimeGenerated, time_window), TimeGenerated, SubjectLogonId
| join kind=inner(
SecurityEvent
| where TimeGenerated > ago(timeframe)
| where EventID == 4663
| where Process has_any ("java.exe", "javaw.exe")
| where AccessMask in ('0x2','0x100', '0x10', '0x4')
| where ObjectName endswith ".jsp" 
| summarize by ParentProcessName, Account, Computer, ObjectName, ProcessName, timekey= bin(TimeGenerated, time_window), TimeGenerated, SubjectLogonId)
 on timekey, Computer, SubjectLogonId

Leg 2: `DeviceFileEvents`

DeviceFileEvents 
| where InitiatingProcessFileName has_any ("java.exe", "javaw.exe")  
| where InitiatingProcessCommandLine has "SysAidServer"  
| where FileName endswith ".jsp" 
| extend Account = strcat(InitiatingProcessAccountDomain, @'\', InitiatingProcessAccountName), Computer = DeviceName

Leg 3: `imFileEvent`

imFileEvent
| where TimeGenerated > ago(timeframe)
| where EventType == "FileCreated"
| where ActingProcessName has_any ("java.exe", "javaw.exe") 
| where ActingProcessCommandLine has "SysAidServer"  
| where FilePath endswith ".jsp" 
| extend Account = ActorUsername, Computer = DvcHostname

Applied to the combined result

| extend AccountName = tostring(split(Account, @'\')[1]), AccountNTDomain = tostring(split(Account, @'\')[0])
| extend HostName = tostring(split(Computer, ".")[0]), DomainIndex = toint(indexof(Computer, '.'))
| extend HostNameDomain = iff(DomainIndex != -1, substring(Computer, DomainIndex + 1), Computer)

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
`AccessMask`	in	`0x10` transforms: `cased` `0x100` transforms: `cased` corpus 5 (sigma 2, splunk 2, elastic 1) `0x2` transforms: `cased` corpus 4 (sigma 2, splunk 2) `0x4` transforms: `cased`
`ActingProcessCommandLine`	match	`SysAidServer` transforms: `term`
`ActingProcessName`	match	`java.exe` `javaw.exe`
`CommandLine`	match	`SysAidServer` transforms: `term`
`EventID`	eq	`4663` transforms: `cased` corpus 34 (splunk 29, kusto 5) `4688` transforms: `cased` corpus 313 (splunk 283, kusto 30)
`EventType`	eq	`FileCreated` transforms: `cased` corpus 8 (kusto 8)
`FileName`	ends_with	`.jsp`
`FilePath`	ends_with	`.jsp`
`InitiatingProcessCommandLine`	match	`SysAidServer` transforms: `term`
`InitiatingProcessFileName`	match	`java.exe` `javaw.exe`
`ObjectName`	ends_with	`.jsp`
`Process`	match	`java.exe` `javaw.exe`

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
`Account`	`summarize`
`Computer`	`summarize`
`ObjectName`	`summarize`
`ParentProcessName`	`summarize`
`ProcessName`	`summarize`
`SubjectLogonId`	`summarize`
`TimeGenerated`	`summarize`
`timekey`	`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)

Identify SysAid Server web shell creation

MITRE ATT&CK coverage

Event coverage

Rule body kusto

Stages and Predicates

Parameters

union `isfuzzy=true` (3 sources)

Leg 1: `SecurityEvent`

Leg 2: `DeviceFileEvents`

Leg 3: `imFileEvent`

Applied to the combined result

Indicators

Output fields

Keyboard shortcuts

Search operators

Identify SysAid Server web shell creation

MITRE ATT&CK coverage

Event coverage

Rule body kusto

Stages and Predicates

Parameters

union isfuzzy=true (3 sources)

Leg 1: SecurityEvent

Leg 2: DeviceFileEvents

Leg 3: imFileEvent

Applied to the combined result

Indicators

Output fields

union `isfuzzy=true` (3 sources)

Leg 1: `SecurityEvent`

Leg 2: `DeviceFileEvents`

Leg 3: `imFileEvent`