Windows: Suspicious Run Key from Download

Rule ID

PH_Rule_SIGMA_670

Default Status

Enabled

Description

Detects the suspicious RUN keys created by software located in Download or temporary Outlook/Internet Explorer directories. This rule is adapted from https://github.com/SigmaHQ/sigma/blob/master/rules/windows/registry/registry_event/registry_event_susp_download_run_key.yml

Severity

MITRE ATT&CK® Tactics

Persistence

Persistence consists of techniques that adversaries use to keep access to systems across restarts, changed credentials, and other interruptions that could cut off their access. Techniques used for persistence include any access, action, or configuration changes that let them maintain their foothold on systems, such as replacing or hijacking legitimate code or adding startup code.

https://attack.mitre.org/tactics/TA0003

MITRE ATT&CK® Techniques

T1547.001

Boot or Logon Autostart Execution: Registry Run Keys / Startup Folder

Adversaries may achieve persistence by adding a program to a startup folder or referencing it with a Registry run key. Adding an entry to the "run keys" in the Registry or startup folder will cause the program referenced to be executed when a user logs in. Adversaries can use these configuration locations to execute malware, such as remote access tools, to maintain persistence through system reboots. Adversaries may also use Masquerading to make the Registry entries look as if they are associated with legitimate programs.

https://attack.mitre.org/techniques/T1547/001

Impacts

Server

Data Source

Windows Sysmon via FortiSIEM Agent

Detection

Correlation

Remediation Guidance

No remediation guidance specified

Time Window

If the following pattern or patterns match an ingested event within the given time window in seconds, trigger an incident.

300 seconds

Trigger Conditions

If the following defined pattern/s occur within a 300 second time window.

Filter

SubPattern Definitions

SubPattern Name: Filter

This is the named definition of the event query, this is important if multiple subpatterns are defined to distinguish them.

SubPattern Query

This is the query logic that matches incoming events

eventType REGEXP "Win-Sysmon-12-Registry-.*|Win-Sysmon-13-Registry-.*|Win-Sysmon-14-Registry-.*" AND procName REGEXP ".*\\Downloads\\.*|.*\\Local Settings\\Temporary Internet Files\\.*|.*\\Temporary Internet Files\\Content\.Outlook\\.*" AND regKeyPath REGEXP ".*\\SOFTWARE\\Microsoft\\Windows\\CurrentVersion\\Run\\.*"

Group by Attributes

This defines how matching events are aggregated, only events with the same matching attribute values are grouped into one unique incident ID

hostName,procName,regKeyPath

Aggregate Constraint

This is most typically a numerical constraint that defines when the rule should trigger an incident

COUNT(*) >= 1

Incident Attribute Mapping

This section defines which fields in matching raw events should be mapped to the incident attributes in the resulting incident.

The available raw event attributes to map are limited to the group by attributes and the aggregate event constraint fields for each subpattern

hostName = Filter.hostName,
procName = Filter.procName,
regKeyPath = Filter.regKeyPath

FortiSIEM Rules