Is it safe to use open wireless access points?
I sometimes get questions when people use my wireless access point, which, for as long as I can remember, has been open to everyone; that is without any form of password protection or encryption. I arguably don't use the access point much myself, as I prefer the wired connection for the higher bandwidth, security and reliability it provides.
Apart from convenience for myself and visitors, the main reason why I leave my wireless access open is that I believe in a free (both as in beer and freedom) internet, built with principles of solidarity rather than exploitation and profitability. In these days of ubiquitous surveillance, freedom often goes hand in hand with anonymity, which implies providing free internet access to everyone.
I also believe that, as more and more services get perniciously transferred to the global internet, access to the network is becoming a basic human right. This is therefore my small contribution to the struggle, now also part of the Réseau Libre project.
So here were my friends question, in essence:
My credit card info was stolen when I used a wifi hotspot in an airport... Should I use open wifi networks?
Is it safe to use my credit card for shopping online?
Here is a modified version of an answer I sent to a friend recently which I thought could be useful to the larger internet community. The short answer is "sorry about that", "it depends, you generally can, but be careful" and "your credit card company is supposed to protect you".
Sorry!
First off, sorry to hear that our credit card was stolen in an airport! That has to be annoying... Did the credit card company reimburse you? Normally, the whole point of credit cards is that they protect you in case of theft like this and they are supposed to reimburse you if you credit card gets stolen or abused...
The complexity and unreliability of passwords
Now of course, securing every bit of your internet infrastructure helps in protecting against such attacks. However: there is a trade-off! First off, it does makes it more complicated for people to join the network. You need to make up some silly password (which has its own security problems: passwords can be surprisingly easy to guess!) that you will post on the fridge or worst, forget all the time!
And if it's on the fridge, anyone with a view to that darn fridge, be it one-time visitor or sneaky neighbor, can find the password and steal your internet access (although, granted, that won't allow them to directly spy on your internet connection).
In any case, if you choose to use a password, you should use the tricks I wrote in the koumbit wiki to generate the password and avoid writing it on the fridge.
The false sense of security of wireless encryption
Second, it can also give a false sense of security: just because a wifi access point appears "secure" (ie. that the communication between your computer and the wifi access point is encrypted) doesn't mean the whole connection is secure.
In fact, one attack that can be done against access points is exactly to masquerade as an existing access point, with no security security at all. That way, instead of connecting to the real secure and trusted access point, you connect to an evil one which spies on our connection. Most computers will happily connect to such a hotspot even with degraded security without warning.
It may be what happened at the airport, in fact. Of course this particular attack would be less likely to happen if you live in the middle of the woods than an airport, but it's some important distinction to keep in mind, because the same attack can be performed after the wireless access point, for example by your countryside internet access provider or someone attacking it.
Your best protection for your banking details is to rely on good passwords (for your back account) but also, and more importantly, what we call end-to-end encryption. That is usually implemented using the "HTTPS" with a pad lock icon in your address bar. This ensures that the communication between your computer and the bank or credit card company is secure, that is: that no wifi access point or attacker between your computer and them can intercept your credit card number.
The flaws of internet security
Now unfortunately, even the HTTPS protocol doesn't bring complete security. For example, one attack that can be done is similar to the previous one and that is to masquerade as a legitimate bank site, but either strip out the encryption or even fake the encryption.
So you also need to look at the address of the website you
are visiting. Attackers are often pretty clever and will use many
tricks to hide the real address of the website in the address bar.
To work around this, I always explicitly type my bank website address (https://accesd.desjardins.com/
in my case)
directly myself instead of clicking on links, bookmarks or using a
search engine to find my bank site.
In the case of credit cards, it is much trickier because when you buy stuff online, you end up putting that credit card number on different sites which you do not necessarily trust. There's no good solution but complaining to your credit card company if you believe a website you used has stolen your credit card details. You can also use services like Paypal, Dwolla or Bitcoin that hide your credit card details from the seller, if they support the service.
I usually try to avoid putting my credit card details on sites I do not trust, and limit myself to known parties (e.g. Via Rail, Air Canada, etc). Also, in general, I try to assume the network connection between me and the website I visit is compromised. This forced me to get familiar with online security and use of encryption. It is more accessible to me than trying to secure the infrastructure i am using, because i often do not control it at all (e.g. internet cafes...).
Internet security is unfortunately a hard problem, and things are not
getting easier as more things move online. The burden is on us
programmers and system administrators to create systems that are more
secure and intuitive for our users so, as I said earlier, sorry the
internet sucks so much, we didn't think so many people would join the
acid trip of the 70s. 
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