Microsoft pptp vpn vulnerabilities Exploits in Action

2.1.4 Firewall Rules & Filters:
To make the illustration of the PPTP vulnerabilities easier to perform, no 
firewall was placed in front of the PPTP server for the initial tests. Basically 
Network Topology #1 was used for the first array of lab work. Many other tests 
were performed later on with improved network topographies including DMZs, 
multiple firewalls, etc. For the sake of keeping this already extensive document 
size down, the other configurations are not included in detail for the attack 
examples. The configuration used for these examples includes a VPN server 
acting as it’s own limited packet filtering firewall to the internal corporate LAN, 
PPTP server, and router for the internal LAN to access the Internet.
The firewall rules on the PPTP server were as follows:
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