Awesome
VPN arsenal
VPN pentest tools and scripts
Links
https://www.trustwave.com/Resources/SpiderLabs-Blog/Cracking-IKE-Mission-Improbable-(Part-1)/
https://www.trustwave.com/Resources/SpiderLabs-Blog/Cracking-IKE-Mission-Improbable-(Part-2)/
https://www.trustwave.com/Resources/SpiderLabs-Blog/Cracking-IKE-Mission-Improbable-(Part3)/
http://resources.infosecinstitute.com/vulnvpn/
https://insinuator.net/2013/08/vulnerabilities-attack-vectors-of-vpns-pt-1/
https://nohats.ca/wordpress/blog/2015/05/20/weakdh-and-ike-ipsec/
Fake VPN Server
Papers
http://www.sersc.org/journals/IJAST/vol8/2.pdf and
http://www.radarhack.com/dir/papers/Scanning_ike_with_ikescan.pdf
https://www.giac.org/paper/gcih/541/vpn-aggressive-mode-pre-shared-key-brute-force-attack/104625
https://www.ernw.de/download/pskattack.pdf
https://www.infosec.gov.hk/english/technical/files/vpn.pdf
CVE / Exploits
http://www.securiteam.com/securitynews/5EP0K00G1G.html
https://www.nccgroup.trust/uk/our-research/cisco-ipsec-vpn-implementation-group-name-enumeration/
https://blog.exodusintel.com/2016/02/10/firewall-hacking/
https://zerosum0x0.blogspot.ru/2016/09/reverse-engineering-cisco-asa-for.html
https://www.rapid7.com/db/modules/auxiliary/admin/cisco/cisco_asa_extrabacon
https://github.com/RiskSense-Ops/CVE-2016-6366
https://www.exploit-db.com/exploits/39823/
http://blog.csdn.net/nixawk/article/details/52705184
Tools
http://ikecrack.sourceforge.net/
https://github.com/KMGbully/ikebrute
https://github.com/SpiderLabs/ikeforce
http://svn.unix-ag.uni-kl.de/vpnc/