There are currently multiple applications hosted in a VPC. During monitoring it has been noticed that multiple port scans are coming in from a specific IP Address block. The internal security team has requested that all offending IP Addresses be denied for the next 24 hours.

There are currently multiple applications hosted in a VPC. During monitoring it has been noticed that multiple port scans are coming in from a specific IP Address block. The internal security team has requested that all offending IP Addresses be denied for the next 24 hours.

Which of the following is the best method to quickly and temporarily deny access from the specified IP Address’s.
A . Create an AD policy to modify the Windows Firewall settings on all hosts in the VPC to deny access from the IP Address block.
B . Modify the Network ACLs associated with all public subnets in the VPC to deny access from the IP Address block.
C . Add a rule to all of the VPC Security Groups to deny access from the IP Address block.
D . Modify the Windows Firewall settings on all AMI’S that your organization uses in that VPC to deny access from the IP address block.

View Answer

Answer: B

Explanation:

NACL acts as a firewall at the subnet level of the VPC and we can deny the offending IP address block at the subnet level using NACL rules to block the incoming traffic to the VPC instances. Since NACL rules are applied as per the Rule numbers make sure that this rule number should take precedence over other rule numbers if there are any such rules that will allow traffic from these IP ranges. The lowest rule number has more precedence over a rule that has a higher number.

The IAM Documentation mentions the following as a best practices for IAM users

For extra security, enable multi-factor authentication (MFA) for privileged IAM users (users who are allowed access to sensitive resources or APIs). With MFA, users have a device that generates a unique authentication code (a one-time password, or OTP). Users must provide both their normal credentials (like their user name and password) and the OTP. The MFA device can either be a special piece of hardware, or it can be a virtual device (for example, it can run in an app on a smartphone).

Options C is invalid because these options are not available

Option D is invalid because there is not root access for users

For more information on IAM best practices, please visit the below URL:

https://docs.IAM.amazon.com/IAM/latest/UserGuide/best-practices.html

The correct answer is: Modify the Network ACLs associated with all public subnets in the VPC to deny access from the IP Address block.

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