What are the disadvantages of Tor?

Question

I've just started using Tor recently, and I'm not sure exactly what security issues come with the benefits.

What should/shouldn't I be worried about (in both everyday normal-web browsing use, in visiting hidden services, and in running my own)?

-- A bit of background for this question; what specifically prompted it --

I'm planning on going live with a rough web site for person/professional use within the next couple weeks, and I want it to be well-protected, but at the same time able to be remotely administered.

I do plan to actually harden the webserver (and use a strong SSH password, login to an account with as little privilege as possible, etc.), but I have no idea whether exclusively doing SSH administration over Tor would be a useful level of misdirection, or would just open me up to possibly undesirable attention from people monitoring the Tor network.

edit: The guy who mentioned 'Tor is just for anonymity' is correct. I guess I should rephrase that last bit: From what I've read, it seems like I wouldn't need to configure my router to forward all requests to the SSH port if I made SSH only available through Tor. If that's the case, it would mean fewer people would be able to access the port, because fewer would be aware of it, and it would be easier to see irregularities in the server logs. It would be more for the purpose of defense-in-depth and making maintenance easier than anything else. However, since I'm not sure what the disadvantages might be, I'm asking this question to clarify.

Answer 1

1. Performance sucks

   It's better than a couple of years ago, but still not great.

2. Low latency anonymizers are prone to traffic analysis.

   In particular if somebody can observe your traffic and your target's traffic, they can correlate that.

   Anonymous remailers avoid this problem by adding longer delays, but you can't use them for interactive applications, such as browsing the web.

3. Exit nodes see your traffic in plain

   If you don't use a secure protocol on top of Tor, the exit node can sniff your passwords etc. Using SSL or SSH you should be fine, but be sure to validate the certificate/fingerprints.

   This doesn't apply to using hidden services, since there is no exit node, and MitM attacks are prevented by the fingerprint in the domain. But be careful that you're accessing the correct domain, they're pretty hard to memorize/verify.

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One interesting variant is connecting to a VPN over Tor. That helps with 3), provided you trust the VPN, but you need to figure out a way to buy VPN access anonymously.

Answer 2

SSH is very sensitive to latency, since every single key stroke implies a round-trip to the server. Doing SSH over a high-latency link is a recipe for high levels of frustrations. I already find more than 200 ms of latency unbearable after a few minutes of SSH -- with Tor, you'll get much more. That point alone will make you regret considering Tor several times per day.

As for the security benefits... well, you used the expressions "misdirection" and "fewer would be aware of it". That's security through obscurity, which is not very popular in these parts. Such measures do not bring much security overall (and, worse, do not bring quantifiable security). They will deter amateur attackers who are not knowledgeable or not very motivated; but these small fry attackers would not have been a big threat anyway. The real danger lies in powerful, competent attackers who will make the effort to do a bit of research on their target, and, for instance, find this very security.SE post where you argue, in plain words, about restricting access to Tor users. In any case, competent attackers will use Tor, if only to hide their tracks. Therefore, a case could be made about not restricting SSH access to Tor users, but quite the opposite: block SSH access from Tor.

If you want "misdirection" just to keep your log files smaller, set the SSH server to a port distinct from the standard 22. It would be a grave error to believe that it increases security, but it will avoid the thousands of daily connection attempts from botnet which try to extend their territory in a purely automated fashion; thus, you will keep smaller log files and correspondingly increase your chances of spotting fishy business in the said log files.

For security, use SSH key-based authentication and/or good, very random passwords.

Answer 3

If I understand you correctly, your objective is to use Tor to increase the security of the communications channel between yourself and your web server?

Tor's main purpose is anonymity. It does not secure the communications channel between the exit node and the destination. Proper use of SSH (use a passphrase) should be more than adequate.

The only reason you would want to use Tor in this scenario is if you need to hide the fact that you're admin-ing a particular server. Based on your description, this isn't a consideration, so just use SSH.

Answer 4

Have you looked into other alternatives? Like a internet based VPN? If the other site is under your own control you can that do easily, by configuring your end point filtering devices.

A default VPN setup provides higher assurance then TOR for that matter.

If you are looking for remote admin, I think bandwidth for you would matter. I think TOR gives you variable delays, whereas with VPN it's a measured and fixed delay, and therefore better for performance.