How can I brute-force PPTP passwords? What tools are available?

Two approaches are mentioned: using `thc-pptp-bruter` (available in Kali) for dictionary attacks, or writing a Python script that calls `pptpsetup` and checks for a `ppp0` interface after a 10-second wait to determine success. The Python method handles cases where `thc-pptp-bruter` fails. Both techniques are explained with code in Penetration Techniques - Acquisition and Brute-Force of PPTP Passwords.