MITRE ATT&CK coverage
| Tactic | Techniques |
|---|---|
| Initial Access |
Rule body
id: 8e9d1f70-d529-4598-9d3e-5dd5164d1d02
name: Cisco WSA - Unexpected file type
description: |
'Detects unexpected file type.'
severity: Medium
status: Available
requiredDataConnectors:
- connectorId: SyslogAma
datatypes:
- Syslog
queryFrequency: 1h
queryPeriod: 1h
triggerOperator: gt
triggerThreshold: 0
tactics:
- InitialAccess
relevantTechniques:
- T1189
query: |
CiscoWSAEvent
| where isnotempty(AmpFileName)
| where isempty(AmpThreatName)
| where ResponseBodyMimeType =~ 'application/octet-stream'
| where AmpFileName !endswith '.exe'
| extend IPCustomEntity = SrcIpAddr, AccountCustomEntity = SrcUserName
entityMappings:
- entityType: IP
fieldMappings:
- identifier: Address
columnName: IPCustomEntity
- entityType: Account
fieldMappings:
- identifier: Name
columnName: AccountCustomEntity
version: 1.0.2
kind: Scheduled
Stages and Predicates
Stage 1: source
CiscoWSAEvent
Stage 2: where
| where isnotempty(AmpFileName)
Stage 3: where
| where isempty(AmpThreatName)
Stage 4: where
| where ResponseBodyMimeType =~ 'application/octet-stream'
Stage 5: where
| where AmpFileName !endswith '.exe'
Stage 6: extend
| extend IPCustomEntity = SrcIpAddr, AccountCustomEntity = SrcUserName
Exclusions
The rule actively suppresses these predicates.
| Field | Kind | Excluded values | Search |
|---|---|---|---|
AmpFileName | ends_with | .exe | excludes:AmpFileName field:"AmpFileName" value:".exe" |
Indicators
These rows show field, operator, and value matches.
| Field | Kind | Values | Search |
|---|---|---|---|
AmpFileName | is_not_null | field:"AmpFileName" kind:is_not_null | |
AmpThreatName | is_null | field:"AmpThreatName" kind:is_null | |
ResponseBodyMimeType | eq |
| field:"ResponseBodyMimeType" kind:eq value:"application/octet-stream" |
Output fields
These fields are emitted when the rule matches.
| Field | Source |
|---|---|
AccountCustomEntity | extend |
IPCustomEntity | extend |