IMPORTANT: No additional bug fixes or documentation updates will be released for this version. For the latest information, see the current release documentation.

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Microsoft IIS Connection Strings Decryption

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Microsoft IIS Connection Strings Decryption

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Identifies use of aspnet_regiis to decrypt Microsoft IIS connection strings. An attacker with Microsoft IIS web server access via a webshell or alike can decrypt and dump any hardcoded connection strings, such as the MSSQL service account password using aspnet_regiis command.

Rule type: eql

Rule indices:

winlogbeat-*
logs-endpoint.events.*
logs-windows.*

Severity: high

Risk score: 73

Runs every: 5 minutes

Searches indices from: now-9m (Date Math format, see also Additional look-back time)

Maximum alerts per execution: 33

References:

Tags:

Elastic
Host
Windows
Threat Detection
Credential Access

Version: 5 (version history)

Added (Elastic Stack release): 7.10.0

Last modified (Elastic Stack release): 8.2.0

Rule authors: Elastic

Rule license: Elastic License v2

Investigation guide

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## Config

If enabling an EQL rule on a non-elastic-agent index (such as beats) for versions <8.2, events will not define `event.ingested` and default fallback for EQL rules was not added until 8.2, so you will need to add a custom pipeline to populate `event.ingested` to @timestamp for this rule to work.

Rule query

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process where event.type in ("start", "process_started") and
(process.name : "aspnet_regiis.exe" or process.pe.original_file_name
== "aspnet_regiis.exe") and process.args : "connectionStrings" and
process.args : "-pdf"

Threat mapping

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Framework: MITRE ATT&CK^TM

Tactic:
- Name: Credential Access
- ID: TA0006
- Reference URL: https://attack.mitre.org/tactics/TA0006/
Technique:
- Name: OS Credential Dumping
- ID: T1003
- Reference URL: https://attack.mitre.org/techniques/T1003/

Rule version history

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Version 5 (8.2.0 release)

Formatting only

Version 4 (7.12.0 release)

Formatting only

Version 3 (7.11.2 release)

Formatting only

Version 2 (7.11.0 release)

Updated query, changed from:

event.category:process and event.type:(start or process_started) and
(process.name:aspnet_regiis.exe or
process.pe.original_file_name:aspnet_regiis.exe or
winlog.event_data.OriginalFileName:aspnet_regiis.exe) and
process.args:(connectionStrings and "-pdf")

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