Cisco Cloud Security - Connection to Unpopular Website Detected

Status: available
Severity: medium
Time window: 14d
Source: github.com/Azure/Azure-Sentinel

'Detects first connection to an unpopular website (possible malicious payload delivery).'

MITRE ATT&CK coverage

Tactic	Techniques
Command & Control	`T1071.001` Application Layer Protocol: Web Protocols
Exfiltration	`T1041` Exfiltration Over C2 Channel

Rule body

id: 75297f62-10a8-4fc1-9b2a-12f25c6f05a7
name: Cisco Cloud Security - Connection to Unpopular Website Detected
description: |
  'Detects first connection to an unpopular website (possible malicious payload delivery).'
severity: Medium
status: Available
requiredDataConnectors:
  - connectorId: CiscoUmbrellaDataConnector
    dataTypes:
      - Cisco_Umbrella_proxy_CL
queryFrequency: 1d
queryPeriod: 14d
triggerOperator: gt
triggerThreshold: 0
tactics:
  - CommandAndControl
  - Exfiltration
relevantTechniques:
  - T1071.001
  - T1041
query: |
  let top_million_list = Cisco_Umbrella
  | where EventType == "proxylogs"
  | extend Hostname = parse_url(UrlOriginal)["Host"]
  | summarize count() by tostring(Hostname)
  | top 1000000 by count_
  | summarize make_list(Hostname);
  Cisco_Umbrella
  | where EventType == "proxylogs"
  | extend Hostname = parse_url(UrlOriginal)["Host"]
  | where Hostname !in (top_million_list)
  | extend Message = "Connect to unpopular website (possible malicious payload delivery)"
  | project TimeGenerated, Message, SrcIpAddr, DstIpAddr, UrlOriginal 
entityMappings:
  - entityType: URL
    fieldMappings:
      - identifier: Url
        columnName: UrlOriginal
  - entityType: IP
    fieldMappings:
      - identifier: Address
        columnName: SrcIpAddr
version: 1.1.3
kind: Scheduled

Stages and Predicates

Let binding: `top_million_list` used in Stage 4

let top_million_list = Cisco_Umbrella
| where EventType == "proxylogs"
| extend Hostname = parse_url(UrlOriginal)["Host"]
| summarize count() by tostring(Hostname)
| top 1000000 by count_
| summarize make_list(Hostname);

Stage 1: `source`

Cisco_Umbrella

Stage 2: `where`

| where EventType == "proxylogs"

Stage 3: `extend`

| extend Hostname = parse_url(UrlOriginal)["Host"]

Stage 4: `where`

| where Hostname !in (top_million_list)

Stage 5: `extend`

| extend Message = "Connect to unpopular website (possible malicious payload delivery)"

Stage 6: `project`

| project TimeGenerated, Message, SrcIpAddr, DstIpAddr, UrlOriginal

Exclusions

The rule actively suppresses these predicates.

Field	Kind	Excluded values	Search
`Hostname`	eq	`top_million_list`	`excludes:Hostname` `field:"Hostname" value:"top_million_list"`

Indicators

These rows show field, operator, and value matches.

Field	Kind	Values	Search
`EventType`	eq	`proxylogs`	`field:"EventType" kind:eq value:"proxylogs"`

Output fields

These fields are emitted when the rule matches.

Field	Source
`DstIpAddr`	`project`
`Message`	`project`
`SrcIpAddr`	`project`
`TimeGenerated`	`project`
`UrlOriginal`	`project`

Cisco Cloud Security - Connection to Unpopular Website Detected

MITRE ATT&CK coverage

Rule body

Stages and Predicates

Let binding: top_million_list used in Stage 4

Stage 1: source

Stage 2: where

Stage 3: extend

Stage 4: where

Stage 5: extend

Stage 6: project