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I will be connecting my laptop in an untrusted network. If I setup OpenVpn on a server and use a vpn client on the laptop to connect through it, is it enough? Can someone perform a MITM attack or otherwise eavesdrop on my traffic?

If someone on the local network port-scans my laptop, will the open ports be accessible to him while I use the VPN tunnel?

Is there anything else I should keep in mind?

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closed as off topic by Wesley, MDMarra, EEAA, Michael Hampton, Chris S Dec 15 '12 at 3:56

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I'm no expert at this (though I use VPN each day), so I won't officially answer, but I'm pretty sure that connecting from an open network to a secured one via VPN (e.g., VPN to work while on ATT-WIFI at Starbucks), your VPN is no less secure than if you were in a protected network at home/work. –  orokusaki Dec 15 '12 at 3:34
    
A Man in the Middle Attack is one of those great ones that very nearly everything is vulnerable to. Some systems, such as SSL and Kerberos, attempt to mitigate it in some ways, but nothing can be perfect. –  Scott Pack Dec 15 '12 at 3:35
    
I can only wonder as to the downvote... –  john Dec 15 '12 at 3:45
    
Your question does not appear to be on topic for Server Fault as written. You may find certain aspects of your question better asked at some of our sister sites, such as Super User or IT Security. Be sure to check the site's FAQ prior to posting to ensure that your question is on topic, and search for existing questions as well. (Oh, I didn't downvote either...) –  Michael Hampton Dec 15 '12 at 3:53
    
@john I did not downvote, but I can attempt to wonder. If you hover over the down arrow, you'll see the tip that says "Does not show any research effort, is unclear, or not useful." If I were to speculate I would say that you've offended someone who does not believe you've done much or any research effort. The answers to your questions are VPN 101 and ServerFault is intended for professionals that either would know those answers, or have a base of knowledge and research faculties that would be able to find these answers with self directed study. Just my opinion on the downvote. –  Wesley Dec 15 '12 at 3:54

1 Answer 1

up vote 3 down vote accepted

If I setup OpenVpn on a server and use a vpn client on the laptop to connect through it, is it enough?

It's impossible to say since we don't know what you're required specifications are. Let's be safe and just say "no."

Can someone perform a MITM attack or otherwise eavesdrop on my traffic?

Yes. No. Maybe. It depends on the encryption and negotiation types of the VPN.

If someone on the local network port-scans my laptop, will the open ports be accessible to him while I use the VPN tunnel?

Yes. A VPN connection merely allows your PC to have an added route to a different network, and all communication over that network be secured to one degree or another. Your PC is still just as visible on any network that it is physically connected to, either via a wired or wireless connection.

Is there anything else I should keep in mind?

Yes. That VPNs and the broader spectrum of network security are complex things that need to have much time given to the pursuit of in-depth knowledge.

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Required specifications? No eavesdropping and protection from port-scanning inside the untrusted network. From your answer, I understand the second is not what VPN is designed to do, so I 'll figure another way for that. But I don't understand the "Yes.No. Maybe" answer regarding the encryption and negotiation types.Practically, OpenVpn uses insecure encryption? –  john Dec 15 '12 at 3:43
    
@john: I think you'll find this to be an excellent learning opportunity. Some starter questions: What underlying encryption mechanism does OpenVPN use to set up the encrypted tunnel? Does it offer configurable cipher suites, key lengths, etc. –  Scott Pack Dec 15 '12 at 3:45
    
@ScottPack [%]D<(^_^<) <-- Have a beer, good sir. –  Wesley Dec 15 '12 at 3:46
    
@ScottPack: I think I don't want to do I semester on Cryptography before using OpenVpn. I 'm not trying to protect the Dead Sea Scrolls here... –  john Dec 15 '12 at 3:48
    
@john You don't have to either, but as a professional, implementing something you don't have a cursory understanding of is negligent. Even the Wikipedia article might be deep enough, though in the interests of full disclosure I haven't looked. –  Scott Pack Dec 15 '12 at 4:07

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