Many of you by now will have read about the Apple security issues in iOS and Mac OS X. Whilst we all wait patiently for Apple to comment on the issue, or better yet to fix it, users are left exposed to a bug that could allow attackers to gain access to sensitive information. I thought therefore that it was worth spending a few moments talking about the ways to mitigate this problem and an innovative unofficial patch from a colleague, Paul Ducklin, who writes for Naked Security at Sophos. If you want to skip right to the tips scroll down a little further in the article.
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For those of you whom are technically inclined Paul has put together an excellent technical analysis of the fault here, but for the rest of us, here is a quick summary of how an attacker could use this flaw to attack:
- An attacker must cause a client to connect to them – this could be trivially achieved by creating a wireless hotspot and letting them connect.
- The attacker must force the client to negotiate a specific protocol version and feature. This is easy as the attacker, or the server in this instance is the one that specifies this.
- The attacker redirects the client from their requested site and provides a somewhat legitimate looking certificate. As if my magic the certificate is accepted.
To paint the picture of how easy this would be, in a recent test in San Francisco we set up our own wireless hotspot offering free Internet (named FreePublicWifi and FreeInternet) and within a short space of time 1512 users connected voluntarily. Any one of these users who wanted our free Internet connection could potentially have been targeted. As a side, we were able to detect from these systems that 484 of these systems were using iOS and 181 using Mac OS X (I would have argued a little high, but I suppose this is expected in San Francisco). This shows how realistic this attack vector actually is and how easy it would have been for us to execute this attack. Note, we offered a warning and did not modify traffic or doing anything malicious – but it would have been easy to not play nice.
What should you do about it?
- Naturally, when Apple releases a fix you should apply it. Unfortunately, whilst the patch is available for iOS users tend to be very tardy in actually applying patches to their systems. Friends don’t let friends use unlatched devices with nasty bugs.
- Don’t join untrustworthy wireless networks. How do you know that networks like ‘Starbucks’, ‘Free Internet’ or ‘attwifi’ aren’t just nasty copies set up by an attacker? Try to stick to networks you know and trust to reduce the risk.
- Use a VPN to encrypt your traffic. A VPN will forward all of your exchanges through it in a tunnel preventing the attacker from exploiting the bug. It also has the benefit that it will cover all of the additional applications beyond Safari waiting to be fixed.
- Use web filtering, general endpoint security and follow broader security best practice. Naturally, if an attacker does pull off this attack they may want to deploy malicious code and other layers of security will help detect this if it does occur. You may also want to take a look at my article on password security here and make sure your passwords are not common across multiple sites to restrict exposure.
One more option (warning, technical gore included)
Paul has done some very interesting research on the failure and for those of you who are interested in the technical flaw and how it could be mitigated. Take a look here. I wouldn’t recommend production deployment of this fix, but it does show in depth where the flaw occurs and how it can be mitigated. It is very much worth the read from a research perspective for those of you that want a little more detail about what mistake was actually made.
We will all wait on Apple providing further updates, but in the mean time make sure you apply these best practices and think a little more carefully about what you connect to.
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