Comprehensive Guide to Twitter Privacy: Where are you?

Comprehensive Guide to Twitter Privacy

I've become fascinated with how Twitter has such simple settings, and yet Twitter privacy is in many ways quite complex, so I'm starting to put all of this information together. This is part 2 of... a bunch.

[Part 1: Who hears what you say?]
[Part 2: Where are you?] <-- you are here!

Now read on to learn How your iPhone may be letting people know where you live and what being responsible about sharing your location really entails!

Part 2: Where are you?

A year ago, I talked about How Foursquare can help people steal your stuff. Someone had set up a handy site called PleaseRobMe.com which let you search to find out who in a given area wasn't at home based on their Foursquare checkins. (The site now says the the authors have made their point about oversharing and have disabled the search.)

The point being that while sharing your location can be a neat way to meet up with friends, it can also be used in dangerous ways. So whether it's Foursquare, Yelp, Facebook Places, Google Latitude, or Twitter, you need to think about what you're sharing and why.

Twitter's built-in location settings

At the time I wrote about PleaseRobMe.com, I don't think location was built into Twitter, but it's since been made an option for any Twitter post. I have to say, that I really love how twitter has done to make this option clear... including doing their best to make it possible to recover from an "oops" moment where you realise you've been sharing waaay too much information and want to delete all the location data to be safe:

They've also done a nice job with the "Learn more" help document, which includes the following message:

Be cautious and careful about the amount of information you share online. There may be some updates where you want to share your location ("The parade is starting now." or "A truck just spilled delicious candy all over the roadway!"), and some updates where you want to keep your location private. Just like you might not want to tweet your home address, please be cautious in tweeting coordinates you don't want others to see.

That pretty much sums up the advice any security/privacy expert would give you, although the complete document also explains how to turn things on and off, when one might prefer a precise location and when one might prefer just the city, etc.

But just like with the tweet privacy settings we talked about in part 1, this isn't the only way your location can be shared. Only this time, we're not going to blame your followers... we're going to blame your camera.

How your iPhone may be telling everyone where you live

Many modern smartphones and cameras, including the iPhone, have a GPS built-in such that you can store location data with every photo. That's pretty cool when it comes to sorting photos later, but because this information is stored with a photo, each picture you share could potentially tell someone exactly where you are (or were when you took the photo).

In Cybercasing the Joint: On the Privacy Implications of Geo-Tagging, Friedland and Sommer started looking at how many people share location data, whether they did so in unsafe ways, and whether they were aware of what information they were sharing. I highly recommend you flip through their HotSec presentation to look at the examples. (Even better if you can catch them presenting -- I really enjoyed seeing that presentation in person! -- but the slides are pretty informative on their own.)

My favourite one involves William Shatner accidentally revealing a "secret" studio location when he posted about recording there! And perhaps more relevant to "cybercasing the joint" are the craigslist posts that show expensive items, their exact geolocation, and the list of times when someone will be at home to take a phone call from an interested buyer.

The issue here is that geodata is often recorded by default. And it can even be dangerous to share this information. As a parent, how would you feel if you realized your teenage daughter had been taking photos of herself in her bedroom and it turned out that any predator could figure out where she lived? How do you feel about the fact that your friends' photos from your last party may have told everyone on the internet where you live?

Many photo services, such as Twitpic and Flickr, allow you to generalize your data so that it shows up as being in a city without showing precisely where within that city. But if you choose to have it visible (or just don't hide the data), you can often get a nice map where you can zoom in:

On Flickr you can view the exif data (Exchangeable image file format -- basically extended meta-information for pictures of the photo) and get the coordinates there...

All ready for someone's stalking pleasure!

The moral of this story

Sharing your location can be scary, and protecting your location privacy doesn't stop at turning off location on Twitter or refusing to sign in to Foursquare/Facebook places/Yelp. If you don't want everyone to know exactly where you are, you also have to make sure your camera and your friends' cameras aren't giving the game away.

Stay tuned for more Twitter privacy posts in April! And in case you missed it, here's [Part 1: Who hears what you say?] which talks about tweet privacy.

Comprehensive Guide to Twitter Privacy: Who hears what you say?

Comprehensive Guide to Twitter Privacy

I've become fascinated with how Twitter has such simple settings, and yet Twitter privacy is in many ways quite complex, so I'm starting to put all of this information together. This is part 1 of... many.

[Part 1: Who hears what you say?] <-- you are here! [Part 2: Where are you?]

Note that many of the things I'm saying here are true of other social networks or any place you might share information online, but I decided this would be most readable with examples from one site, so I've decided to use Twitter, which I like and use regularly.

Part 1: Who hears what you say?

On the surface, Twitter has perhaps the simplest privacy policy of any social network:

Either everyone can read your tweets (everything you say on twitter is public) or you can make your feed private (and then maintain a list of people who are allowed to see it).

You also, regardless of which option you choose, have the option of blocking individuals from following you. Blocking someone isn't hugely effective if they can then log out and read your public feed anyhow, but it can cut down on spam.

Retweeting

Blocking everyone you don't know is not necessarily the end of the story. Just like gossip, anyone who can read what you've said can also share it. It's fairly common in twitter parlance to "retweet" a message: that is, repeat the message verbatim or sometimes with small edits for length or the addition of commentary.

When you have a public account, retweeting is pretty much harmless behaviour. Anyone could see that funny thing you said if they looked, so if one of your followers retweets it, you're really just winding up with a few more strangers seeing it than you might otherwise. But they could have looked at that tweet at any time if they so chose. Often it's a really positive thing: more people get to hear about a cause you believe in or something cool you've done.

However, the story can be quite different if you have a private account. Perhaps you have chosen to keep your account private because you and your boss don't share political views. That "funny" thing you said could become seriously awkward if she winds up seeing it retweeted. Probably you chose to make your account private for a reason, and retweets can violate your expectation of privacy.

Violating privacy with retweets?

There's actual a whole paper on this subject that appeared in Web 2.0 Security and Privacy 2010. It has the cheesy-cute title RT @IWantPrivacy: Widespread Violation of Privacy Settings in the Twitter Social Network. They found that while some clients did block users from retweeting private feeds, many didn't and of course users could always just type RT and repeat the whole message anyhow. The researchers collected 4.42 million tweets that were exposing private information in this manner, and they expect that the numbers will continue to climb.

It's hard to tell, however, whether those millions of exposed tweets were really problematic for the people who wound up exposed, however. Perhaps millions of people asked before retweeting (something you should always do before sharing private information, but I know even I forget to do this sometimes when telling a good story I heard, so I suspect retweeting is no different). Perhaps most of the tweets were cute pictures of cats that no one really minded sharing. But either way, you should be aware of what you retweet and aware of what you say that could be retweeted.

Retweeting lies

It's also worth noting that even though researchers assumed that most of those tweets were actual privacy exposures, it's equally possible that many of them were made up. If someone can type RT and your name and cut and paste in the message, there's no reason that it has to be your message that they post in. Often edits are minor, but there's nothing stopping one from going RT @twitter we hate kittens or something significantly more damaging to someone's reputation. Without a public feed, it's hard to refute since no one can check what you said, and even with a public feed people may expect that you deleted the offending message. A recent defamation lawsuit in the US may serve as a reminder that what you say and what you seem to say on twitter could have real implications.

So that little checkbox? It's clearly not the end of the story.

Stay tuned for Part 2 next week!

[Part 1: Who hears what you say?] <-- you are here! [Part 2: Where are you?]

Privacy and Twitter lists

I think twitter may have among the simplest privacy settings of any social network. Your choices are either everything you post is public, or everything you post is private.

But simple does not mean that things will stay private. Just like everything on the internet, the minute you post something someone else might choose to share it. Some researchers have actually studied how often people retweet private content on Twitter.

Something I haven't seen studied, however, is how private information can leak out through twitter lists.

Twitter allows you to make lists of people who you'd like to have grouped together. For example, I have a list of technical women who I follow. These are women in technology who I've met in person or interacted with extensively online, and I really made it for my own personal use but since it's a public list others can (and do) follow it. Presumably they're looking for more cool women to expand their social networks.

Twitter allows you to see what lists a person has been added to, and this is where it gets interesting. Let's take a look at the lists of which I am a member and see what we can learn about me.

Here's a few things you can get a glance:

• I have a lot of real-life friends on twitter (and now you know many of them are)
• I'm a musician
• I work in security, technology and on open source software
• I'm speaking at an upcoming conference and have attended a variety of events
• My friend Leigh is stalking me ;)
• I live in Ottawa

Wait... what? Despite the fact that I explicitly chose to say a more generic "Canada" in my profile information, my current city can be determined by the fact that it shows up in several of the lists I'm on. There's of course no way to be sure that any of this is true, but when more than one person lists me as being in Ottawa it seems fairly reasonable to guess.

I'm not personally concerned (obviously, since I'm talking about all this information in a public blog post!) but some folk are much more private than I am.

So what are your options if you want to hide this information? Well, if I don't like the lists I'm on, I can... uh... There's no apparent way to leave a twitter list. I suspect one could block the list curator, but the people revealing your location are most likely to be actual real life friends: people you wouldn't want to block. So you'd have to resort to asking nicely, but that's assuming you even notice: while you can get notifications of new followers, you do not get notified when you're added to a list. I've been asked about exactly two of the lists I've been put on (thanks @ghc!) so obviously it's not the social norm to ask (I certainly have never asked anyone I've listed!)

A quick check says I can usually get the current (and sometimes some former) cities for many of my friends, as well as information related to their occupations, interests, and events they've attended. For most of these people, I know this isn't information they consider private either. But it's obviously possible that this could be a problem... I wonder how many people it affects in a negative way?

Maybe this is a potential little workshop paper if I have time to analyse a whole bunch of twitter lists. Anyone want to lend me a student who's interested in social media privacy?

Edit: A note for those concerned about not being that privacy-violating friend. You can make twitter lists private if you want (it's just not the default), so just do that for the lists you think are sensitive and you're good to go!

A crash course in the social media equivalent of defensive driving

How can you stay safe and keep things private while still taking part in online life? I'm a web security researcher, so I get asked this fairly frequently.  And it's easy to see how people get overwhelmed by all the news stories, the marketing blurbs, and the constantly changing policies.

Why I'm not telling you to quit Facebook

Let's say you're worried about your risk of getting into a car accident.  Do you sell your car and refuse to get into any moving vehicle?  No.  Refusing to use a car might make you safer, but it would be quite isolating and, depending on where and how you live, very difficult.  Just like many people live without cars, you can live without social networking, but it there are some significant costs to refusing to participate.  Many people's need or desire to participate is much stronger that the risks they face.

If you're worried about car accidents, you've got other options to manage your risks than giving up your car.  You can learn to drive defensively.  You can make sure you wear your seatbelt.  You can learn about the safety ratings and use cars that perform better in safety tests.  You can refuse to drive places that are dangerous.

So what I'm hoping to do here is give you a crash course in the social media equivalent of defensive driving.

The web is not a safe place

When I learned to drive, my driving instructor often reminded me that I had to treat every car on the road as if it were being driven by a moron who might swerve into my lane at any time.   It might seem like a very negative point of view, but it's a very practical one that's helped me avoid accidents on numerous occasions simply because I was expecting it.

My blog is called Web Insecurity for a reason.  Nearly 2/3 of web pages currently have a serious vulnerability.  So that means no matter what the policy is, how careful you are, or how careful your friends are... there's a good chance you are going to view some code controlled by a bad guy, and they could get information about you that you don't want them to have.  It's often very easy to exploit these vulnerable parts of a website.  75% of websites with malicious code are legitimate sites.   

You may be thinking, "sure, but no one's going to care about my data."  And you may be right.  But if a bad guy is trying to make a company look terrible, one way to do so is to expose information about all of their users.  You can definitely wind up as collateral damage.

Learn your legal protections

Learning about legal stuff can be time-consuming and confusing, and frankly companies may violate laws anyhow.  But it's still worth learning a bit about your rights. The EFF has quite an impressive body of work covering free speech, privacy, intellectual property and other important issues, and they do a great job of translating legal speak into clear, comprehensible articles.   You might also consider reading bloggers like Michael Geist, and your country may have great resources like the Office of the Privacy Commissioner of Canada.

Remember that things that may seem similar often have very different legal protections.  For example, if my credit card number is stolen, there are laws that limit my liability to $50.   But that's not true about all money transactions online:  Debit/bank cards have no such legal protection.  Some modern credit cards that require a PIN have no such protection even though these cards aren't actually safe. You may have no legal protection from your bank if you don't follow their security procedure to the letter, and those security requirements of online banks can be pretty crazy: Do you reboot your computer every time you bank?  No?  You might be on the hook if someone compromises your account!

So yeah.  It's a bit of work, but it's worth it to at least learn about the issues that affect you.

Learn the controls

It may seem a bit silly, given that I've already told you that websites can easily be compromised, but if you're managing risks you should learn to use your privacy controls, choose good passwords and security questions, and keep those things private.  Again, it's about managing your risks: even if these controls can't make you 100% safe, they might make you safer.


Companies are not your friends

For many companies online, you are not really their primary customer: your time and your personal information are assets the company sells to their advertisers.  You have to expect to be treated accordingly. You have to treat every company or organization you interact with online as potential hazards.   Many companies intentionally or unintentionally violate privacy laws and even violate their own privacy rules.  And privacy rules change, sometimes because the company itself changed them, sometimes because they get bought out by another company.  Your guarantee when you signed up for the site is unlikely to hold a year from now, but it may be nigh impossible to remove your data from the system when it changes.

And that's just the "legitimate" problems that could affect you: there's a good chance any company's sites could be attacked and your data exposed as a result -- it happens to fully legitimate companies all the time, no matter how good their intentions towards you and your data.

Choose your friends wisely

You wouldn't tell all your secrets to the office gossip, but online your friends may be "forced" to become gossips either through malicious software or through changing policies.  It sounds like some crazy super-spy movie: trust no one!  Your friends could be compromised!  But once again, just like I'm not telling you to delete your facebook account, I'm not going to tell you not to share, just to be defensive.

For example, I have a couple of friends who really enjoy Facebook games.  They seem to install every new thing that comes along and invite me to join.  Nothing wrong with that, right?  I mean, if I don't want to join, I just don't, and that's the end of it.  Except that it's not: my friends have all these games and thus all these extra ways that someone might break in to their accounts.  And indeed, these are the folk who wind up with compromised accounts more often than most.   So while these are great people who I'd be happy to share job concerns or relationship woes with in real life... It's too risky for me to share private stuff with them online.  They are the office gossips, whether they mean to be or not.  They're not the only ones who put me at risk (any friend can end up on the wrong end of a broken website) but they're the riskiest.

Choose what you want to share

The biggest part of managing your risk is choosing what you want to share online.  Here's a few questions you might want to ask yourself:

1. Will this embarrass me if it gets out?
2. Will this affect my safety?
3. Will this affect my employment?
4. Will this affect my family/friends?

If your job requires you to be a role model, you may have to be a role model even in your off-hours. Maybe it shouldn't be that way, but let's be pragmatic: you have to assume that it is that way.  

You have to assume that anything you share online could become public knowledge.  You can't trust the companies, you can't assume their sites are safe, and you can't even trust your friends because of unsafe websites.  

Think before you share.

Using a pen name

One other way to manage risk is to use a pen name or pseudonym.  Lots of people do this to give them a layer of privacy, especially when trying out something new like starting a silly blog, or when engaging in discussion that could be sensitive such as online political debate.  Sometimes it's even an open secret that so-and-so goes by a nickname online, and the only reason they do is to make it harder for potential employers to come up with a list of everything they do online when searching their legal name and given email address.

This is a great tool if you want some more freedom to speak, but people sometimes will do the legwork necessary to figure out who you are, especially if you're high-profile or saying something unpopular.  So pen names are great, but do remember that they're not 100% guaranteed to keep you safe.  Again, it's another way to manage risks.

No matter what you do, everything may become public

I've said this a bunch of different ways, but this is the real take-home message here: No matter how careful you are, anything you do online can become public knowledge.   It's up to you to manage your risks accordingly.

But don't despair -- it may sound stupidly hard, but you're already handling issues of trust and privacy every time you choose to tell a story to a friend or complain about work at a party.  You might have to pretend you're in a spy movie and trust no one, or you might decide some things are perfectly fine to share with the world.  Just try to make an informed decision.