Windows: Findstr LSASS

Rule ID

PH_Rule_SIGMA_2309

Default Status

Enabled

Description

Detects findstr commands that include the keyword lsass, which indicates recon actviity for the LSASS process PID. Local Security Authority Subsystem Service (LSASS.exe), which manages system-level authentication. Findstr is a very powerful command line tool that makes it easy to search through files and folders based on criteria missing in the standard File Explorer search. This rule is adapted from https://github.com/SigmaHQ/sigma/blob/master/rules/windows/process_creation/proc_creation_win_findstr_lsass.yml

Severity

MITRE ATT&CK® Tactics

Credential Access

Credential Access consists of techniques for stealing credentials like account names and passwords. Techniques used to get credentials include keylogging or credential dumping. Using legitimate credentials can give adversaries access to systems, make them harder to detect, and provide the opportunity to create more accounts to help achieve their goals.

https://attack.mitre.org/tactics/TA0006

MITRE ATT&CK® Techniques

T1552.006

Unsecured Credentials: Group Policy Preferences

Adversaries may attempt to find unsecured credentials in Group Policy Preferences (GPP). GPP are tools that allow administrators to create domain policies with embedded credentials. These policies allow administrators to set local accounts.

https://attack.mitre.org/techniques/T1552/006

Impacts

Server

Data Source

Windows Sysmon via FortiSIEM Agent

Detection

Correlation

Remediation Guidance

Determine if this was an authorized penetration testing activity or authorized sysadmin activity. Otherwise, there is no reason for this activity to be occurring. The host should be quarantined and investigated immediately. Collect the process hash and check for malware match. Investigate what other incidents are occurring on that host during that time frame.

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="Win-Sysmon-1-Create-Process" AND (((procName REGEXP "\\findstr\.exe$" OR srcFileName="FINDSTR.EXE") AND command REGEXP ".*lsass.*") OR command REGEXP ".* /i \"lsass.*|.* /i lsass\.exe.*|.*findstr \"lsass.*|.*findstr lsass.*|.*findstr\.exe \"lsass.*|.*findstr\.exe lsass.*")

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

command,hostName,procName,srcFileName

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

command = Filter.command,
hostName = Filter.hostName,
procName = Filter.procName,
srcFileName = Filter.srcFileName

FortiSIEM Rules