Excessive Uncommon DNS Queries

Rule ID

PH_Rule_Flow_17

Default Status

Enabled

Description

Detects the same host that is not a DNS server, doing an excessive amount of uncommon domain name queries - this indicates the host is likely infected with malware. An end host typically needs to perform only A and PTR queries; any other query inidicates the likely presence of malware.

Severity

MITRE ATT&CK® Tactics

Exfiltration

Exfiltration consists of techniques that adversaries may use to steal data from your network. Once they’ve collected data, adversaries often package it to avoid detection while removing it. This can include compression and encryption. Techniques for getting data out of a target network typically include transferring it over their command and control channel or an alternate channel and may also include putting size limits on the transmission.

https://attack.mitre.org/tactics/TA0010

MITRE ATT&CK® Techniques

T1048.002

Exfiltration Over Alternative Protocol: Exfiltration Over Asymmetric Encrypted Non-C2 Protocol

Adversaries may steal data by exfiltrating it over an asymmetrically encrypted network protocol other than that of the existing command and control channel. The data may also be sent to an alternate network location from the main command and control server.

https://attack.mitre.org/techniques/T1048/002

Impacts

Application

Data Source

Microsoft DNS via FortiSIEM Agent, BIND DNS via Syslog,InfoBlox NiOS via Syslog, Cisco Umbrella via AWS_S3,Cisco Umbrella via HTTPS_ADVANCED (Umbrella API)

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.

UncommonDNS

SubPattern Definitions

SubPattern Name: UncommonDNS

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

srcIpAddr NOT IN (Group@PH_SYS_APP_DNS_SERVER) AND eventType NOT IN (Group@PH_SYS_EVENT_CommonDNSTraffic) AND (eventType CONTAIN "BIND_DNS" OR eventType CONTAIN "MS_DNS")

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

srcIpAddr,eventType

Aggregate Constraint

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

COUNT (*) >= 50

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

 srcIpAddr = UncommonDNS.srcIpAddr,
 incidentCount =UncommonDNS.COUNT (*)

FortiSIEM Rules