Excessive Amount of Denied Connections from a Single Source

Status: available
Severity: medium
Time window: 5m
Group by: Src_IP
Source: github.com/Azure/Azure-Sentinel

'This creates an incident in the event that a single source IP address generates a excessive amount of denied connections.'

MITRE ATT&CK coverage

Tactic	Techniques
Impact	`T1499` Endpoint Denial of Service

Rule body

id: 3d645a88-2724-41a7-adea-db74c439cf79
name: Excessive Amount of Denied Connections from a Single Source
description: |
  'This creates an incident in the event that a single source IP address generates a excessive amount of denied connections.'
severity: Medium
status: Available
requiredDataConnectors:
  - connectorId: SyslogAma
    datatypes:
      - Syslog
queryFrequency: 1h
queryPeriod: 1h
triggerOperator: gt
triggerThreshold: 0
tactics:
  - Impact
relevantTechniques:
  - T1499
query: |
  let threshold = 5000;
  SophosXGFirewall
  | where Log_Type =~ "Firewall" and Status =~ "Deny"
  | summarize count() by Src_IP, bin(TimeGenerated,5m)
  | where count_ > threshold
entityMappings:
  - entityType: IP
    fieldMappings:
      - identifier: Address
        columnName: Src_IP
version: 1.0.4
kind: Scheduled

Stages and Predicates

Parameters

let threshold = 5000;

Stage 1: `source`

SophosXGFirewall

Stage 2: `where`

| where Log_Type =~ "Firewall" and Status =~ "Deny"

Stage 3: `summarize`

| summarize count() by Src_IP, bin(TimeGenerated,5m)

Stage 4: `where`

| where count_ > threshold

Indicators

These rows show field, operator, and value matches.

Field	Kind	Values	Search
`Log_Type`	eq	`Firewall`	`field:"Log_Type" kind:eq value:"Firewall"`
`Status`	eq	`Deny`	`field:"Status" kind:eq value:"Deny"`
`count_`	gt	`5000`	`field:"count_" kind:gt value:"5000"`

Output fields

These fields are emitted when the rule matches.

Field	Source
`Src_IP`	`summarize`