Windows: Suspicious Cobalt Strike DNS Beaconing

Rule ID

PH_Rule_SIGMA_828

Default Status

Enabled

Description

Detects a program that invoked suspicious DNS queries known from Cobalt Strike beacons. Cobalt Strike (https://www.cobaltstrike.com/) is an adversary simulation tool with a post-exploitation agent and covert channels to emulate a quiet long-term embedded actor in your network. It uses Process injection, a defense evasion technique that runs custom code within the address space of another process, thereby avoiding detection. This rule is adapted from https://github.com/SigmaHQ/sigma/blob/master/rules/windows/dns_query/dns_query_win_mal_cobaltstrike.yml

Severity

MITRE ATT&CK® Tactics

Command And Control

MITRE ATT&CK® Techniques

T1071.004

Application Layer Protocol: DNS

Adversaries may communicate using the Domain Name System (DNS) application layer protocol to avoid detection/network filtering by blending in with existing traffic. Commands to the remote system, and often the results of those commands, will be embedded within the protocol traffic between the client and server.

https://attack.mitre.org/techniques/T1071/004

Impacts

Server

Data Source

Windows Sysmon via FortiSIEM Agent

Detection

Correlation

Remediation Guidance

Cobalt Strike / Meterpreter are intended to be used by penetration testers and security red teams to simulate a real cyberthreat. Investigate whether the user needs to really run Cobalt Strike or Meterpreter. Investigate what other incidents are occurring on that host during that time frame. 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-22-DNS-Query" AND (queryId REGEXP "^aaa\.stage\.|^post\.1" OR queryId REGEXP ".*\.stage\.123456\..*")

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,queryId

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,
queryId = Filter.queryId

FortiSIEM Rules