An attempt was made to modify AWS EC2 snapshot attributes. Snapshots are sometimes shared by threat actors in order to exfiltrate bulk data from an EC2 fleet. If the permissions were modified, verify the snapshot was not shared with an unauthorized or unexpected AWS account.
Rule type: query
Risk score: 47
Runs every: 10m
Maximum alerts per execution: 100
- Continuous Monitoring
- Asset Visibility
Rule license: Elastic License v2
## Triage and analysis ### Investigating AWS EC2 Snapshot Activity Amazon EC2 snapshots are a mechanism to create point-in-time references to data that reside in storage volumes. System administrators commonly use this for backup operations and data recovery. This rule looks for the modification of snapshot attributes using the API `ModifySnapshotAttribute` action. This can be used to share snapshots with unauthorized third parties, giving others access to all the data on the snapshot. #### Possible investigation steps - Identify the user account that performed the action and whether it should perform this kind of action. - Search for dry run attempts against the resource ID of the snapshot from other user accounts within CloudTrail. - Investigate other alerts associated with the user account during the past 48 hours. - Assess whether this behavior is prevalent in the environment by looking for similar occurrences involving other users. - Contact the account owner and confirm whether they are aware of this activity. - Considering the source IP address and geolocation of the user who issued the command: - Do they look normal for the calling user? - If the source is an EC2 IP address, is it associated with an EC2 instance in one of your accounts or is the source IP from an EC2 instance that's not under your control? - If it is an authorized EC2 instance, is the activity associated with normal behavior for the instance role or roles? Are there any other alerts or signs of suspicious activity involving this instance? - Check if this operation was approved and performed according to the organization's change management policy. - Check if the shared permissions of the snapshot were modified to `Public` or include unknown account IDs. - If you suspect the account has been compromised, scope potentially compromised assets by tracking servers, services, and data accessed by the account in the last 24 hours. ### False positive analysis - If this rule is noisy in your environment due to expected activity, consider adding exceptions — preferably with a combination of user and IP address conditions. ### Response and remediation - Initiate the incident response process based on the outcome of the triage. - Disable or limit the account during the investigation and response. - Identify the possible impact of the incident and prioritize accordingly; the following actions can help you gain context: - Identify the account role in the cloud environment. - Assess the criticality of affected services and servers. - Work with your IT team to identify and minimize the impact on users. - Identify if the attacker is moving laterally and compromising other accounts, servers, or services. - Identify any regulatory or legal ramifications related to this activity. - Investigate credential exposure on systems compromised or used by the attacker to ensure all compromised accounts are identified. Reset passwords or delete API keys as needed to revoke the attacker's access to the environment. Work with your IT teams to minimize the impact on business operations during these actions. - Check if unauthorized new users were created, remove unauthorized new accounts, and request password resets for other IAM users. - Consider enabling multi-factor authentication for users. - Review the permissions assigned to the implicated user to ensure that the least privilege principle is being followed. - Implement security best practices [outlined](https://aws.amazon.com/premiumsupport/knowledge-center/security-best-practices/) by AWS. - Take the actions needed to return affected systems, data, or services to their normal operational levels. - Identify the initial vector abused by the attacker and take action to prevent reinfection via the same vector. - Using the incident response data, update logging and audit policies to improve the mean time to detect (MTTD) and the mean time to respond (MTTR).
event.dataset:aws.cloudtrail and event.provider:ec2.amazonaws.com and event.action:ModifySnapshotAttribute
Framework: MITRE ATT&CKTM