Zscaler Private Access (ZPA) , CHATTR Linux, Immuable, VPC -> PrefixList

https://superuser.com/questions/1647896/putty-key-format-too-new-when-using-ppk-file-for-putty-ssh-key-authentication

VPC -> PrefixList
https://docs.aws.amazon.com/vpc/latest/userguide/managed-prefix-lists.html

https://aws.amazon.com/marketplace/pp/prodview-epy3md7fcvk4g?ref=cns_srchrow

https://www.fugue.co/blog/cloud-network-security-101-aws-security-groups-vs-nacls

https://www.javatpoint.com/aws-nacl-vs-security-group

https://mylearningsonline.com/aws-services/aws-vpc-security-group-nacl/

https://www.davidc.net/sites/default/subnets/subnets.html

http://www.cronmaker.com/

https://www.baeldung.com/linux/grep-sed-awk-differences#1-basic-syntax-1

chattr +i      [To make it immutable, Its not related to access permissions] - Change Attribute

SetUserBit

SetGroupBit                       chmod 2775          chmod +ug rw

which                                 Which executable

whereis

https://stackoverflow.com/questions/39239276/how-to-enable-a-directory-listing-in-apache-web-server