Microsoft IIS Connection Strings Decryption

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:

Severity: high

Risk score: 73

Runs every: 5m

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

Maximum alerts per execution: 33

References:

Tags:

Version: 8

Rule authors:

Rule license: Elastic License v2

## Setup

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.

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"