Windows: ISO File Created Within Temp Folders

Rule ID

PH_Rule_SIGMA_1962

Default Status

Enabled

Description

Detects the creation of a ISO file in the Outlook temp folder or in the Appdata temp folder. Typical of Qakbot TTP from end-July 2022. This rule is adapted from https://github.com/SigmaHQ/sigma/blob/master/rules/windows/file/file_event/file_event_win_iso_file_mount.yml

Severity

MITRE ATT&CK® Tactics

Initial Access

Initial Access consists of techniques that use various entry vectors to gain their initial foothold within a network. Techniques used to gain a foothold include targeted spearphishing and exploiting weaknesses on public-facing web servers. Footholds gained through initial access may allow for continued access, like valid accounts and use of external remote services, or may be limited-use due to changing passwords.

https://attack.mitre.org/tactics/TA0001

MITRE ATT&CK® Techniques

T1566.001

Phishing: Spearphishing Attachment

Adversaries may send spearphishing emails with a malicious attachment in an attempt to elicit sensitive information and/or gain access to victim systems. Spearphishing attachment is different from other forms of spearphishing in that it employs the use of malware attached to an email. Upon opening the attachment (and potentially clicking past protections), the adversary's payload exploits a vulnerability or directly executes on the user's system. Adversaries frequently manipulate file extensions and icons in order to make attached executables appear to be document files, or files exploiting one application appear to be a file for a different one.

https://attack.mitre.org/techniques/T1566/001

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="Win-Sysmon-11-FileCreate" AND fileName REGEXP "\.iso$" AND ((fileName REGEXP ".*\\AppData\\Local\\Temp\\.*" AND fileName REGEXP ".*\.zip\\.*") OR fileName REGEXP ".*\\AppData\\Local\\Microsoft\\Windows\\INetCache\\Content\.Outlook\\.*")

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

fileName,hostName

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

fileName = Filter.fileName,
hostName = Filter.hostName

FortiSIEM Rules