Windows: Compress Data and Lock With Password for Exfiltration With 7-ZIP

Rule ID

PH_Rule_SIGMA_1525

Default Status

Enabled

Description

Detects 7zip utilities to compress and encrypt data. An adversary may compress or encrypt data that is collected prior to exfiltration using 3rd party utilities. This rule is adapted from https://github.com/SigmaHQ/sigma/blob/master/rules/windows/process_creation/proc_creation_win_7zip_password_compression.yml

Severity

MITRE ATT&CK® Tactics

Collection

Collection consists of techniques adversaries may use to gather information and the sources information is collected from that are relevant to following through on the adversary's objectives. Frequently, the next goal after collecting data is to steal (exfiltrate) the data. Common target sources include various drive types, browsers, audio, video, and email. Common collection methods include capturing screenshots and keyboard input.

https://attack.mitre.org/tactics/TA0009

MITRE ATT&CK® Techniques

T1560.001

Archive Collected Data: Archive via Utility

An adversary may compress or encrypt data that is collected prior to exfiltration using 3rd party utilities. Many utilities exist that can archive data, including 7-Zip, WinRAR, and WinZip. Most utilities include functionality to encrypt and/or compress data.

https://attack.mitre.org/techniques/T1560/001

Impacts

Server

Data Source

Windows Sysmon via FortiSIEM Agent

Detection

Correlation

Remediation Guidance

Legitimate activity is expected since compressing files with a password is common. Determine if the process being launched is expected or otherwise benign behavior. If necessary, rebuild the host from a known, good source and have the user change their password.

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 (description REGEXP ".*7-Zip.*" OR procName REGEXP "\\7z\.exe$|\\7za\.exe$|\\7zr\.exe$" OR srcFileName IN ("7z.exe","7za.exe")) AND command REGEXP ".* -p.*" AND command REGEXP ".* a .*|.* u .*"

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,description,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,
description = Filter.description,
hostName = Filter.hostName,
procName = Filter.procName,
srcFileName = Filter.srcFileName

FortiSIEM Rules