Cisco ASA - average attack detection rate increase

Status: available
Severity: low
Time window: 6h
Group by: DeviceEventClassID, DeviceName, DropRate, SourceIP, SourceOfDropRateCount
Source: github.com/Azure/Azure-Sentinel

'This will help you determine if Cisco ASA devices are under heavier attack than normal over the last hour versus the previous 6 hours based on DeviceEventClassID 733100 References: https://www.cisco.com/c/en/us/td/docs/security/asa/syslog/b_syslog/syslogs9.html Details on how to further troubleshoot/investigate: https://www.cisco.com/c/en/us/support/docs/security/asa-5500-x-series-next-generation-firewalls/113685-asa-threat-detection.html'

MITRE ATT&CK coverage

Tactic	Techniques
Discovery	`T1046` Network Service Discovery
Impact	`T1498` Network Denial of Service

Rule body

id: 79f29feb-6a9d-4cdf-baaa-2daf480a5da1
name: Cisco ASA - average attack detection rate increase
description: |
  'This will help you determine if Cisco ASA devices are under heavier attack than normal over the last hour versus the previous 6 hours based on DeviceEventClassID 733100
  References: https://www.cisco.com/c/en/us/td/docs/security/asa/syslog/b_syslog/syslogs9.html
  Details on how to further troubleshoot/investigate: https://www.cisco.com/c/en/us/support/docs/security/asa-5500-x-series-next-generation-firewalls/113685-asa-threat-detection.html'
severity: Low
status: Available
requiredDataConnectors:
  - connectorId: CiscoAsaAma
    dataTypes:
      - CommonSecurityLog
queryFrequency: 1h
queryPeriod: 6h
triggerOperator: gt
triggerThreshold: 0
tactics:
  - Discovery
  - Impact
relevantTechniques:
  - T1046
  - T1498
query: |
  let timeframe = 1h;
  let last1h = CommonSecurityLog
  | where TimeGenerated >= ago(timeframe)
  | where isempty(CommunicationDirection)
  | where DeviceEventClassID == "733100"
  | extend SourceOfDropRateCount = tostring(split(tostring(split(Message, "]")[0]),"[ ")[1])
  | extend splitMessage = split(Message, ".")
  | extend DropRate = tostring(split(tostring(splitMessage[0]),"] ")[1])
  | extend CurrentBurstRate = split(tostring(split(tostring(splitMessage[1]),"  ")[0]),"is ")
  | extend CurrentBurstRatePerSec = toint(split(tostring(CurrentBurstRate[1])," ")[0])
  | extend MaxConfiguredBurstRate = toint(CurrentBurstRate[2])
  | extend CurrentAvgRate = split(tostring(split(tostring(splitMessage[1]),"  ")[1]),"is ")
  | extend CurrentAvgRatePerSec = toint(split(tostring(CurrentAvgRate[1])," ")[0])
  | extend MaxConfiguredAvgRate = toint(CurrentAvgRate[2])
  | extend CumulativeTotal = toint(split(tostring(split(tostring(splitMessage[1]),"  ")[2]),"is ")[1])
  | summarize last1hCumTotal = sum(CumulativeTotal), last1hAvgRatePerSec = avg(CurrentAvgRatePerSec), last1hAvgBurstRatePerSec = avg(CurrentBurstRatePerSec) by DeviceName, DeviceEventClassID, SourceIP, SourceOfDropRateCount, DropRate;
  let prev6h = CommonSecurityLog
  | where TimeGenerated between (ago(6h) .. ago(1h))
  | where isempty(CommunicationDirection)
  | where DeviceEventClassID == "733100"
  | extend SourceOfDropRateCount = tostring(split(tostring(split(Message, "]")[0]),"[ ")[1])
  | extend splitMessage = split(Message, ".")
  | extend DropRate = tostring(split(tostring(splitMessage[0]),"] ")[1])
  | extend CurrentBurstRate = split(tostring(split(tostring(splitMessage[1]),"  ")[0]),"is ")
  | extend prevCurrentBurstRatePerSec = toint(split(tostring(CurrentBurstRate[1])," ")[0])
  | extend prevMaxConfiguredBurstRate = toint(CurrentBurstRate[2])
  | extend CurrentAvgRate = split(tostring(split(tostring(splitMessage[1]),"  ")[1]),"is ")
  | extend prevCurrentAvgRatePerSec = toint(split(tostring(CurrentAvgRate[1])," ")[0])
  | extend prevMaxConfiguredAvgRate = toint(CurrentAvgRate[2])
  | extend prevCumulativeTotal = toint(split(tostring(split(tostring(splitMessage[1]),"  ")[2]),"is ")[1])
  | summarize StartTimeUtc = min(TimeGenerated), EndTimeUtc = max(TimeGenerated), prev6hCumTotal = sum(prevCumulativeTotal), prev6hAvgRatePerSec = avg(prevCurrentAvgRatePerSec), prev6hAvgBurstRatePerSec = avg(prevCurrentBurstRatePerSec)
  by DeviceName, DeviceEventClassID, SourceIP, SourceOfDropRateCount, DropRate;
  last1h | join (
    prev6h
  ) on DeviceName, DeviceEventClassID, SourceIP, SourceOfDropRateCount, DropRate
  | project StartTimeUtc, EndTimeUtc, DeviceName, DeviceEventClassID, SourceIP, SourceOfDropRateCount, DropRate, last1hCumTotal, prev6hCumTotal, prev6hAvgCumTotal = prev6hCumTotal/6, last1hAvgRatePerSec, prev6hAvgRatePerSec, last1hAvgBurstRatePerSec, prev6hAvgBurstRatePerSec
  // Select only events that indicate a doubling of the expected rate in the last hour over the previous 6 hours
  | where last1hCumTotal > 2*prev6hAvgCumTotal or last1hAvgRatePerSec > 2*prev6hAvgRatePerSec or last1hAvgBurstRatePerSec > 2*prev6hAvgBurstRatePerSec
  | extend HostName = tostring(split(DeviceName, ".")[0]), DomainIndex = toint(indexof(DeviceName, '.'))
  | extend HostNameDomain = iff(DomainIndex != -1, substring(DeviceName, DomainIndex + 1), DeviceName)
entityMappings:
  - entityType: Host
    fieldMappings:
      - identifier: FullName
        columnName: DeviceName
      - identifier: HostName
        columnName: HostName
      - identifier: DnsDomain
        columnName: HostNameDomain
  - entityType: IP
    fieldMappings:
      - identifier: Address
        columnName: SourceIP
version: 1.0.3
kind: Scheduled

Stages and Predicates

Stage 0: `let`

let timeframe = 1h;
let last1h = CommonSecurityLog <inlined as stages below>;
let prev6h = CommonSecurityLog
| where TimeGenerated between (ago(6h) .. ago(1h))
| where isempty(CommunicationDirection)
| where DeviceEventClassID == "733100"
| extend SourceOfDropRateCount = tostring(split(tostring(split(Message, "]")[0]),"[ ")[1])
| extend splitMessage = split(Message, ".")
| extend DropRate = tostring(split(tostring(splitMessage[0]),"] ")[1])
| extend CurrentBurstRate = split(tostring(split(tostring(splitMessage[1]),"  ")[0]),"is ")
| extend prevCurrentBurstRatePerSec = toint(split(tostring(CurrentBurstRate[1])," ")[0])
| extend prevMaxConfiguredBurstRate = toint(CurrentBurstRate[2])
| extend CurrentAvgRate = split(tostring(split(tostring(splitMessage[1]),"  ")[1]),"is ")
| extend prevCurrentAvgRatePerSec = toint(split(tostring(CurrentAvgRate[1])," ")[0])
| extend prevMaxConfiguredAvgRate = toint(CurrentAvgRate[2])
| extend prevCumulativeTotal = toint(split(tostring(split(tostring(splitMessage[1]),"  ")[2]),"is ")[1])
| summarize StartTimeUtc = min(TimeGenerated), EndTimeUtc = max(TimeGenerated), prev6hCumTotal = sum(prevCumulativeTotal), prev6hAvgRatePerSec = avg(prevCurrentAvgRatePerSec), prev6hAvgBurstRatePerSec = avg(prevCurrentBurstRatePerSec)
by DeviceName, DeviceEventClassID, SourceIP, SourceOfDropRateCount, DropRate;

Stage 1: `source`

CommonSecurityLog

Stage 2: `where`

| where TimeGenerated >= ago(timeframe)

Stage 3: `where`

| where isempty(CommunicationDirection)

Stage 4: `where`

| where DeviceEventClassID == "733100"

Stage 5: `extend` (10 consecutive steps)

| extend SourceOfDropRateCount = tostring(split(tostring(split(Message, "]")[0]),"[ ")[1])
| extend splitMessage = split(Message, ".")
| extend DropRate = tostring(split(tostring(splitMessage[0]),"] ")[1])
| extend CurrentBurstRate = split(tostring(split(tostring(splitMessage[1]),"  ")[0]),"is ")
| extend CurrentBurstRatePerSec = toint(split(tostring(CurrentBurstRate[1])," ")[0])
| extend MaxConfiguredBurstRate = toint(CurrentBurstRate[2])
| extend CurrentAvgRate = split(tostring(split(tostring(splitMessage[1]),"  ")[1]),"is ")
| extend CurrentAvgRatePerSec = toint(split(tostring(CurrentAvgRate[1])," ")[0])
| extend MaxConfiguredAvgRate = toint(CurrentAvgRate[2])
| extend CumulativeTotal = toint(split(tostring(split(tostring(splitMessage[1]),"  ")[2]),"is ")[1])

Stage 6: `summarize`

| summarize last1hCumTotal = sum(CumulativeTotal), last1hAvgRatePerSec = avg(CurrentAvgRatePerSec), last1hAvgBurstRatePerSec = avg(CurrentBurstRatePerSec) by DeviceName, DeviceEventClassID, SourceIP, SourceOfDropRateCount, DropRate

Stage 7: `join`

| join (
  prev6h
) on DeviceName, DeviceEventClassID, SourceIP, SourceOfDropRateCount, DropRate

Stage 8: `project`

project DeviceEventClassID, DeviceName, DropRate, EndTimeUtc, SourceIP, SourceOfDropRateCount, StartTimeUtc, last1hAvgBurstRatePerSec, last1hAvgRatePerSec, last1hCumTotal, prev6hAvgBurstRatePerSec, prev6hAvgCumTotal, prev6hAvgRatePerSec, prev6hCumTotal

Stage 9: `where`

where (last1hAvgBurstRatePerSec > (prev6hAvgBurstRatePerSec * 2) or last1hAvgRatePerSec > (prev6hAvgRatePerSec * 2) or last1hCumTotal > (prev6hAvgCumTotal * 2))

Stage 10: `extend`

extend DomainIndex, HostName

Stage 11: `extend`

extend HostNameDomain

HostNameDomain =

ifDomainIndex != -1substring(DeviceName, (DomainIndex + 1))

elseDeviceName

Indicators

These rows show field, operator, and value matches.

Field	Kind	Values	Search
`CommunicationDirection`	is_null	(no value, null check)	`field:"CommunicationDirection" kind:is_null`
`DeviceEventClassID`	eq	`733100`	`field:"DeviceEventClassID" kind:eq value:"733100"`
`last1hAvgBurstRatePerSec`	cross_field_compare	`prev6hAvgBurstRatePerSec` transforms: `op:gt`, `rhs:mul:2`	`field:"last1hAvgBurstRatePerSec" kind:cross_field_compare value:"prev6hAvgBurstRatePerSec"`
`last1hAvgRatePerSec`	cross_field_compare	`prev6hAvgRatePerSec` transforms: `op:gt`, `rhs:mul:2`	`field:"last1hAvgRatePerSec" kind:cross_field_compare value:"prev6hAvgRatePerSec"`
`last1hCumTotal`	cross_field_compare	`prev6hAvgCumTotal` transforms: `op:gt`, `rhs:mul:2`	`field:"last1hCumTotal" kind:cross_field_compare value:"prev6hAvgCumTotal"`

Output fields

These fields are emitted when the rule matches.

Field	Source
`DeviceEventClassID`	`project`
`DeviceName`	`project`
`DropRate`	`project`
`EndTimeUtc`	`project`
`SourceIP`	`project`
`SourceOfDropRateCount`	`project`
`StartTimeUtc`	`project`
`last1hAvgBurstRatePerSec`	`project`
`last1hAvgRatePerSec`	`project`
`last1hCumTotal`	`project`
`prev6hAvgBurstRatePerSec`	`project`
`prev6hAvgCumTotal`	`project`
`prev6hAvgRatePerSec`	`project`
`prev6hCumTotal`	`project`
`DomainIndex`	`extend`
`HostName`	`extend`
`HostNameDomain`	`extend`

Cisco ASA - average attack detection rate increase

MITRE ATT&CK coverage

Rule body

Stages and Predicates

Stage 0: let

Stage 1: source

Stage 2: where

Stage 3: where

Stage 4: where

Stage 5: extend (10 consecutive steps)

Stage 6: summarize

Stage 7: join

Stage 8: project

Stage 9: where

Stage 10: extend

Stage 11: extend