Sample rules
Cloud Compute Instance Created With Previously Unseen Instance Type
- source: splunk
- technicques:
Description
The following analytic detects the creation of EC2 instances with previously unseen instance types. The detection is made by using a Splunk query to identify the EC2 instances. First, the query searches for changes in the EC2 instance creation action and filters for instances with instance types that are not recognized or previously seen. Next, the query uses the Splunk tstats command to gather the necessary information from the Change data model. Then, it filters the instances with unknown instance types and reviews previously seen instance types to determine if they are new or not. The detection is important because it identifies attackers attempting to create instances with unknown or potentially compromised instance types, which can be an attempt to gain unauthorized access to sensitive data, compromise of systems, exfiltrate data, potential disruption of services, or launch other malicious activities within the environment. False positives might occur since there might be legitimate reasons for creating instances with previously unseen instance types. Therefore, you must carefully review and triage all alerts.
Detection logic
| tstats earliest(_time) as firstTime, latest(_time) as lastTime values(All_Changes.object_id) as dest, count from datamodel=Change where All_Changes.action=created by All_Changes.Instance_Changes.instance_type, All_Changes.user
| `drop_dm_object_name("All_Changes")`
| `drop_dm_object_name("Instance_Changes")`
| where instance_type != "unknown"
| lookup previously_seen_cloud_compute_instance_types instance_type as instance_type OUTPUTNEW firstTimeSeen, enough_data
| eventstats max(enough_data) as enough_data
| where enough_data=1
| eval firstTimeSeenInstanceType=min(firstTimeSeen)
| where isnull(firstTimeSeenInstanceType) OR firstTimeSeenInstanceType > relative_time(now(), "-24h@h")
| table firstTime, user, dest, count, instance_type
| `security_content_ctime(firstTime)`
| `cloud_compute_instance_created_with_previously_unseen_instance_type_filter`
EC2 Instance Started With Previously Unseen Instance Type
- source: splunk
- technicques:
Description
This search looks for EC2 instances being created with previously unseen instance types. This search is deprecated and have been translated to use the latest Change Datamodel.
Detection logic
`cloudtrail` eventName=RunInstances [search `cloudtrail` eventName=RunInstances errorCode=success
| fillnull value="m1.small" requestParameters.instanceType
| stats earliest(_time) as earliest latest(_time) as latest by requestParameters.instanceType
| rename requestParameters.instanceType as instanceType
| inputlookup append=t previously_seen_ec2_instance_types.csv
| stats min(earliest) as earliest max(latest) as latest by instanceType
| outputlookup previously_seen_ec2_instance_types.csv
| eval newType=if(earliest >= relative_time(now(), "-70m@m"), 1, 0)
| `security_content_ctime(earliest)`
| `security_content_ctime(latest)`
| where newType=1
| rename instanceType as requestParameters.instanceType
| table requestParameters.instanceType]
| spath output=user userIdentity.arn
| rename requestParameters.instanceType as instanceType, responseElements.instancesSet.items{}.instanceId as dest
| table _time, user, dest, instanceType
| `ec2_instance_started_with_previously_unseen_instance_type_filter`