Detection rules › Kusto
Cisco SEG - Multiple large emails sent to external recipient
'Detects possible data exfiltration.'
MITRE ATT&CK coverage
| Tactic | Techniques |
|---|---|
| Exfiltration |
Rule body
id: 1399a9a5-6200-411e-8c34-ca5658754cf7
name: Cisco SEG - Multiple large emails sent to external recipient
description: |
'Detects possible data exfiltration.'
severity: Medium
status: Available
requiredDataConnectors:
- connectorId: CefAma
dataTypes:
- CommonSecurityLog
queryFrequency: 1h
queryPeriod: 1h
triggerOperator: gt
triggerThreshold: 0
tactics:
- Exfiltration
relevantTechniques:
- T1030
query: |
let e_theshold = 3;
let s_threshold = 10000000;
CiscoSEGEvent
| where AdditionalFields[15]['ESAMsgSize'] > s_threshold
| where NetworkDirection =~ 'Outgoing'
| extend rec_domain = extract(@'@(.*)', 1, DstUserName)
| extend s_domain = extract(@'@(.*)', 1, SrcUserName)
| where s_domain != rec_domain
| summarize count() by SrcUserName
| where count_ >= e_theshold
| extend AccountCustomEntity = SrcUserName
entityMappings:
- entityType: Account
fieldMappings:
- identifier: Name
columnName: AccountCustomEntity
version: 1.0.3
kind: Scheduled
Stages and Predicates
Parameters
let e_theshold = 3;
let s_threshold = 10000000;
Stage 1: source
CiscoSEGEvent
Stage 2: where
| where AdditionalFields[15]['ESAMsgSize'] > s_threshold
Stage 3: where
| where NetworkDirection =~ 'Outgoing'
Stage 4: extend
| extend rec_domain = extract(@'@(.*)', 1, DstUserName)
Stage 5: extend
| extend s_domain = extract(@'@(.*)', 1, SrcUserName)
Stage 6: where
| where s_domain != rec_domain
Stage 7: summarize
| summarize count() by SrcUserName
Stage 8: where
| where count_ >= e_theshold
Stage 9: extend
| extend AccountCustomEntity = SrcUserName
Indicators
These rows show field, operator, and value matches.
| Field | Kind | Values | Search |
|---|---|---|---|
ESAMsgSize | gt |
| field:"ESAMsgSize" kind:gt value:"10000000" |
NetworkDirection | eq |
| field:"NetworkDirection" kind:eq value:"Outgoing" |
count_ | ge |
| field:"count_" kind:ge value:"3" |
s_domain | cross_field_compare |
| field:"s_domain" kind:cross_field_compare value:"rec_domain" |
Output fields
These fields are emitted when the rule matches.
| Field | Source |
|---|---|
SrcUserName | summarize |
AccountCustomEntity | extend |