ScreenConnect User Database Modification - Security

Status: test
Severity: medium
Log source: product windows, service security
Author: Matt Anderson, Kris Luzadre, Andrew Schwartz, Huntress
Source: github.com/SigmaHQ/sigma

This detects file modifications to the temporary xml user database file indicating local user modification in the ScreenConnect server. This will occur during exploitation of the ScreenConnect Authentication Bypass vulnerability (CVE-2024-1709) in versions <23.9.8, but may also be observed when making legitimate modifications to local users or permissions. This requires an Advanced Auditing policy to log a successful Windows Event ID 4663 events and with a SACL set on the directory.

MITRE ATT&CK coverage

Tactic	Techniques
Defense Impairment	No specific technique

Event coverage

Provider	Event	Title
Security-Auditing	Event ID 4663	An attempt was made to access an object.

Rule body yaml

title: ScreenConnect User Database Modification - Security
id: 4109cb6a-a4af-438a-9f0c-056abba41c6f
related:
    - id: 1a821580-588b-4323-9422-660f7e131020
      type: similar
status: test
description: |
    This detects file modifications to the temporary xml user database file indicating local user modification in the ScreenConnect server.
    This will occur during exploitation of the ScreenConnect Authentication Bypass vulnerability (CVE-2024-1709) in versions <23.9.8, but may also be observed when making legitimate modifications to local users or permissions.
    This requires an Advanced Auditing policy to log a successful Windows Event ID 4663 events and with a SACL set on the directory.
references:
    - https://www.connectwise.com/company/trust/security-bulletins/connectwise-screenconnect-23.9.8
    - https://www.cve.org/CVERecord?id=CVE-2024-1709
    - https://www.huntress.com/blog/a-catastrophe-for-control-understanding-the-screenconnect-authentication-bypass
author: Matt Anderson, Kris Luzadre, Andrew Schwartz, Huntress
date: 2024-02-20
tags:
    - cve.2024-1709
    - detection.emerging-threats
    - attack.defense-impairment
logsource:
    product: windows
    service: security
    definition: 'Requirements: SACLs must be enabled for the ScreenConnect directory'
detection:
    selection:
        EventID: 4663
        ObjectType: 'File'
        AccessMask: '0x6'
        ObjectName|endswith: '.xml'
        ObjectName|contains|all:
            - 'Temp'
            - 'ScreenConnect'
        ProcessName|contains: 'ScreenConnect.Service.exe'
    condition: selection
falsepositives:
    - This will occur legitimately as well and will result in some benign activity.
level: medium

Stages and Predicates

Stage 0: `condition`

selection

Stage 1: `selection`

selection:
    EventID: 4663
    ObjectType: 'File'
    AccessMask: '0x6'
    ObjectName|endswith: '.xml'
    ObjectName|contains|all:
        - 'Temp'
        - 'ScreenConnect'
    ProcessName|contains: 'ScreenConnect.Service.exe'

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`	eq	`0x6` corpus 3 (sigma 2, kusto 1)
`ObjectName`	ends_with	`.xml`
`ObjectName`	match	`ScreenConnect` `Temp`
`ObjectType`	eq	`File` corpus 10 (sigma 8, splunk 2)
`ProcessName`	match	`ScreenConnect.Service.exe` corpus 2 (sigma 2)

`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)

ScreenConnect User Database Modification - Security

MITRE ATT&CK coverage

Event coverage

Rule body yaml

Stages and Predicates

Stage 0: `condition`

Stage 1: `selection`

Indicators

Keyboard shortcuts

Search operators

ScreenConnect User Database Modification - Security

MITRE ATT&CK coverage

Event coverage

Rule body yaml

Stages and Predicates

Stage 0: condition

Stage 1: selection

Indicators

Stage 0: `condition`

Stage 1: `selection`