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Considering OpenVZ, KVM and Xen:

Which VM technology is the most difficult for the host's administrators to access given an encrypted root partition?

Can I have a reasonable expectation that rogue administrators cannot become root inside my VPS by running a simple command on the host machine?

Which type of VM is most likely to be secure in this scenario?

P.S.: I realise that a VM is never going to offer absolute security and even a dedicated server could theoretically have data siphoned off via RAM.

I'm asking to determine if a VPS is secure enough to handle personal emails capable of resetting passwords or if a dedicated server is necessary and justified considering the increased costs.

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    Encryption doesn't mean much when the attacker has the key. I don't think the issue is how difficult it is, because any competent sysadmin could figure it out. If you choose a virtualized solution, then you should be asking whether Company-X or Company-Y is more secure, not whether Hypervisor-X or Hypervisor-Y is. Commented Jul 28, 2014 at 2:21
  • I've settled on a dedicated server.
    – Crow
    Commented Aug 2, 2014 at 3:55

3 Answers 3

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With KVM and Xen, the rogue administrator can take a snapshot of your live machine, then explore at his leisure what is in the RAM of your VM. In particular, he will easily obtain the encryption keys for the encrypted filesystem, and then proceed to read all your files. By the very nature of the snapshot system, you will not notice it.

With OpenVZ, you don't have a virtual machine but a cheap emulation thereof, with a shared kernel (but that kernel pretends that each user has a whole machine to himself). The host admin has full control over that kernel, and thus can alter it (dynamically) to inspect the RAM of any running process. In any case, if there was disk encryption, it would be done by that kernel.

Either way, it can be done quite easily and silently.


I'm asking to determine if a VPS is secure enough to handle personal emails capable of resetting passwords or if a dedicated server is necessary and justified considering the increased costs.

This entirely depends on what your passwords are protecting. An evil sysadmin will be interested in resetting your passwords only if he has something to gain which will offset the risks (as shown above, reading your emails will be quite risk-free for the attacker, but actually resetting your passwords should attract your attention and may result in trouble for the attacker if he was not careful enough).

Why don't you use Gmail like everybody else ? Google already owns the Internet, after all.

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    I don't use Gmail because: 1. I've had bad experiences with Google Apps. 2. Google have shown time and time again that they do not respect people's information. 3. Google Apps for Business (and Fastmail.fm) is much more expensive than hosting email myself. One user account with Google is $5 whereas a dedicated server with 500GB goes for $8. Since I need to host several domains this works out very well even with a second server and several backups. Thanks for confirming my suspicions that VPS are not suitable for handling personal information, especially when money is involved.
    – Crow
    Commented Aug 2, 2014 at 3:48
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Regardless of what virtualization technology you use. Once the attacker has access to the hardware, it's game over. In case of a VPS, even when encrypting the root partition, if the key is stored in memory and you have no control of the hypervisor, then you cannot protect your system's confidentiality with encryption.

Administrators with access to the hypervisor will always be able to access the machine if the machine is running. For openVZ, considering it's kernel virtualization (administrator will have access to the kernel, you can't protect that it's how it works), it will be a lot less difficult than with KVM or Xen (which is hardware or paravirtualization).

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  • This answers the question nicely. OpenVZ is easier to access than KVM or Xen. No VPS is suitable for private information. Considering this it's alarming how many businesses use EC2, Linode and DigitalOcean to handle personal and business information.
    – Crow
    Commented Aug 2, 2014 at 3:43
  • @Crow AWS has a PCI-DSS compliance (bank level) privacy and security. They've other policies also which prevent them from snooping. If they snoop even a 5$ server and it becomes news, then large customers will flee. It's very risky for them to do that, thankfully :) Commented May 13, 2017 at 18:34
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Use a clean PC or VM for your VPN connection and never ever use that system outside of the VPN.

A VM will only work if your host is clean. If you install free games or random software then you SHOULD NOT trust your PC anymore.

Never login to accounts that you use outside of the VPN !!!

Create separate accounts for any service you use over the VPN. Never login to any of those accounts from any other system!

So, just do it. :)

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    Your answer is off topic. The question is about hosted Virtual Machines and has nothing to do with VPN.
    – Crow
    Commented Aug 2, 2014 at 3:40

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