Using AWS GuardDuty to stop compromised instances and send notifications.

GuardDuty  (announced in the 2017 edition of AWS Re:Invent) , is a managed threat detection service that continuously monitors for malicious or unauthorized behavior to help you protect your AWS accounts and workloads. It monitors for activity such as unusual API calls or potentially unauthorized deployments that indicate a possible account compromise. GuardDuty also detects potentially compromised instances or reconnaissance by attackers.

with a minimal amount of code, and few clicks in the AWS console we can set up guardduty to scan EC2 fleets for eventual threats, notify a lambda function to stop the compromised instances and send an SMS notification using AWS SNS service:

Screen Shot 2018-01-04 at 9.43.11 AM

1- Testing few threats :

1-a – Bitcoin mining : one of the possible threats is using your EC2 instances for bitcoin mining , I started a bitcoind container on my EC2 instance to :

Screen Shot 2018-01-04 at 9.53.26 AM

1-b SSH brute-force : I’m not using any username and passwords dictionaries

Screen Shot 2018-01-04 at 9.55.03 AM

2- SNS topic : create an SNS topic called guardduty_alerts, with an SMS subscription

3- Lambda: for stopping instances and sending notifications

import boto3
import json

def lambda_handler(event, context):
print(‘loading handler’)# print(event)
sns = boto3.client(service_name = “sns”)
topicArn = ‘arn:aws:sns:us-east-1:9999999999:guardduty_alerts’

#
result = json.loads(event)# result is now a dict
instanceId = event[‘detail’][‘resource’][‘instanceDetails’][‘instanceId’]
type = event[‘detail’][‘description’]
message = “your EC2 instance ” + instanceId + “has been compromised by attack of ” + type + “, it will be stopped”
sns.publish(
TopicArn = topicArn,
Message = message
)

ec2 = boto3.client(‘ec2’, region_name = ‘us-east-1’)
ec2.stop_instances(InstanceIds = [instanceId])
return

4- CloudWatch rule: create a cloudwatch rule that triggers the lambda function we created previosly

 

et voila , all the threats that we did earlier shows in the GuardDuty findings :

Screen Shot 2018-01-04 at 10.36.08 AM

Stoping the compromised instances :

Screen Shot 2018-01-04 at 10.42.33 AM

sending notifications:

Screen Shot 2018-01-04 at 10.43.29 AM

 

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