How to block third party VPN?

[stsphiltech]

Good day!
I am working as a Network admin for a small school. Some students were using VPN applications to access blocked sites. Upon checking, I found out that the VPN providers used ports 80, 443 & 5060, which are important ports for browsing and VOIP.
I would like to ask for help on how did you prevent VPN from your network.
Application Control does not prevent VPN to connect from the VPN provider servers.

Thanks and hoping for valuable comments.

[walidk]

i have same issue , i would like to block all vpns , any suggestions

[jcoffin]

VPNs vs firewalls is an arm race. Our signatures for VPNs are updates all the time. The key is to not let the VPN know it is not connected. With Application control, use tarpit instead of block. Tarpit drops the session at the firewall WAN, Block will reply with a reject ACK. If the VPN sees the reject, the VPN will try a different method. It is not possible to stop VPN 100% of the time, but limiting it to low success will deter it's use.