First you have to be aware that the cvpn is kind of a legacy technology and some of the vulnerabilites that IKE has presented in the past might be present on this box, the important part to cover here is to make sure that your box does not have a weak IKE policy enabled which will include DES, MD5 and DH1, if this is an IKE policy that you have enabled then make sure it is disabled since it is easily breakable.
Unfortunately there is no feature on the CVPN that will rate or prevent unknown ike requests but disabling these combinations might help.
As for the study materials you can go ahead and read the users guide for this box.
Table of ContentsIntroductionVersion HistoryPossible Future
UpdatesDocuments PurposeNAT Operation in ASA 8.3+ SectionsRule Types
Network Object NATTwice NAT / Manual NATRule Types used per SectionNAT
Types used with Twice NAT / Manual NAT and Network Obje...
Table of Contents Introduction:This document describes details on how
NAT-T works. Background: ESP encrypts all critical information,
encapsulating the entire inner TCP/UDP datagram within an ESP header.
ESP is an IP protocol in the same sense that TCP an...