Sudden Increase In Firewall Denied Inbound Traffic To A Specific TCP/UDP port

Rule ID

PH_Rule_Stat_6

Default Status

Enabled

Description

Detects anomalous denied inbound traffic profile on a specific TCP/UDP port - over a 30 minute window, both the total number of denies and the number of unique source IP addresses are at least 3 standard deviations away from the mean for the current hour

Severity

MITRE ATT&CK® Tactics

Impact

Impact consists of techniques that adversaries use to disrupt availability or compromise integrity by manipulating business and operational processes. Techniques used for impact can include destroying or tampering with data. In some cases, business processes can look fine, but may have been altered to benefit the adversaries’ goals. These techniques might be used by adversaries to follow through on their end goal or to provide cover for a confidentiality breach.

https://attack.mitre.org/tactics/TA0040

MITRE ATT&CK® Techniques

T1498.001

Network Denial of Service: Direct Network Flood

Adversaries may attempt to cause a denial of service (DoS) by directly sending a high-volume of network traffic to a target. Almost any network protocol may be used for flooding. Stateless protocols such as UDP or ICMP are commonly used but stateful protocols such as TCP can be used as well. Botnets are commonly used to conduct network flooding attacks against networks and services. Large botnets can generate a significant amount of traffic from systems spread across the global Internet. In some of the worst cases for distributed DoS (DDoS), so many systems are used to generate the flood that each one only needs to send out a small amount of traffic to produce enough volume to saturate the target network. In such circumstances, distinguishing DDoS traffic from legitimate clients becomes exceedingly difficult.

https://attack.mitre.org/techniques/T1498/001

Impacts

Network

Data Source

FortiGate via Syslog or Netflow, Cisco IOS via Syslog or Netflow, Checkpoint via Syslog or Netflow, Palo Alto via Syslog or Netflow

Detection

Profiling

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.

1800 seconds

Trigger Conditions

If the following defined pattern/s occur within a 1800 second time window.

StatHighPort

SubPattern Definitions

SubPattern Name: StatHighPort

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

reptDevIpAddr IN (Group@PH_SYS_DEVICE_FIREWALL) AND
	  eventType IN (Group@PH_SYS_EVENT_DenyNetTraffic) AND
	  srcIpAddr NOT IN (Group@PH_SYS_NETWORK_ENTERPRISE_INTERNAL_NET)

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

destIpPort,ipProto

Aggregate Constraint

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

(COUNT(*)-STAT_AVG(COUNT(*):106))/STAT_STDDEV(COUNT(*):106) >= 3  AND
	  STAT_STDDEV(COUNT(*):106) > 0

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

 ipProto = StatHighPort.ipProto,
 destIpPort = StatHighPort.destIpPort,
 totEventCount = StatHighPort.COUNT(*),
 avgTotFlows =StatHighPort.STAT_AVG(COUNT(*):106),
 sdevTotFlows=StatHighPort.STAT_STDDEV(COUNT(*):106)

FortiSIEM Rules