Dropbox lets anyone log in as anyone – so check your files now!

Customers of cloud-based file storing-and-sharing company Dropbox should check on the data they've entrusted to the service, following the company's admission that it messed up its access controls for several hours.

(Updated: please see footnote below.)

Unlike the majority of data breaches we've reported on lately - where usernames and passwords were stolen, allowing attackers and miscreants to access other people's accounts illegally - Dropbox's "hack" was of a more embarrassing sort.

Apparently, Dropbox published a code update which inadvertently removed the need to authenticate. So you could log in to other people's accounts without knowing their passwords at all. (Dropbox isn't alone in having made this sort of mistake. Facebook did something similar last year, leading to Mark Zuckerberg's own fan page being hacked.)

Ouch.

One popular use of services like Dropbox is to get around the restrictions many companies put on emailing around large files. If I'm working at home and have a huge spreadsheet which I know my IT manager won't let through the email gateway, I can just upload it to Dropbox and share the resulting web link with my colleagues.

In theory, the risk of this should be no worse that me copying the file to a USB key and letting my colleagues copy it from there. (In fact, if you're not careful with USB keys, they may pose a larger risk than sharing web links, since the USB key may contain other files - such as malware - besides the spreadsheet you just saved on it.)

But the safety of a web link allowing you to share a file "through the cloud" depends very strongly on who's able to access that link. If anyone can download it, you run the risk of data leakage. And if anyone can access and modify it, you run the risk of something much worse.

Dropbox can also automatically synchronise your own files between all your various devices, such as your desktop PC, your Mac laptop and your smartphone.

In the company's own promotional video, an intrepid adventurer named Josh uses Dropbox to share and to synchronise detailed information between his numerous devices for his forthcoming safari in Africa.

That means that unauthorised access to your Dropbox data could give cybercrooks an enormous amount of information about your life, your plans and your identity. And unauthorised modification of your Dropbox data could propagate incorrect information throughout your digital world.

Dropbox did well to fix the problem within four hours, and to admit this openly on its blog.

But the "eternal beta" flavour of many cloud services - where updates and improvements are rolled out regularly and frequently to suit the service provider rather than its users - is an often-underestimated risk.

By the way, one way to improve the safety of web-based file sharing is to encrypt the files you share before you upload them. Only someone with the password will be able to decrypt those files. And if you don't have the password, you won't be able to alter their content, either.

If you're interested, Sophos has a free tool for Windows users that you can use to encrypt and compress sensitive information. You can use it for free both commercially and personally.

* Download now (direct download, no registration, Windows only)

* Learn more

Footnote. As alert Twitterer Andy Durdin points out, you can readily see if someone else has changed your Dropbox files. But you can't see if someone else has been snooping through your data.

Dropbox suggests on its blog that less than 1% of accounts were accessed during the unprotected period, and that it will contact those users in case the access was unauthorised.

If your account was accessed, be sure to ask Dropbox for a detailed log of what happened so you can find out what got stolen as well as what got changed. Unauthorised access and unauthorised modification are both bad for your digital well-being.

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How to stop your Gmail account being hacked

GmailAs has been widely reported, high profile users of Gmail - including US government officials, reporters and political activists - have had their email accounts hacked.

This wasn't a sophisticated attack against Google's systems, but rather a cleverly-crafted HTML email which pointed to a Gmail phishing page.

Victims would believe that they had been sent an attachment, click on the link, and be greeted by what appeared to be Gmail's login screen. Before you knew it, your Gmail username and password could be in the hands of unauthorised parties.

So, what steps should you take to reduce the chances of your Gmail account being hacked?

  1. Set up Two step verification
  2. Check if your Gmail messages are being forwarded without your permission
  3. Where is your Gmail account being accessed from?
  4. Choose a unique, hard-to-crack password
  5. Secure your computer
  6. Why are you using Gmail anyway?

1. Set up Two step verification

The hackers who broke into high profile Gmail accounts grabbed usernames and passwords. So, an obvious thing to do would be to make Gmail require an extra piece of information before allowing anybody to access your account.

Google provides a facility called "two step verification" to Gmail users, which provides that extra layer of security. It requires you to be able to access your mobile phone when you sign into your email account - as they will be sending you a magic "verification" number via SMS.

The advantage of this approach - which is similar to that done by many online banks - is that even if cybercriminals manage to steal your username and password, they won't know what your magic number is because they don't have your phone.

Google has made two step verification easy to set up.

Setting up 2 step verification

Once you're set up, the next time you try to log into Gmail you'll be asked for your magic number after entering your username and password. Your mobile phone should receive an SMS text message from Google containing your verification number.

Mobile phone receives verification number

Let's just hope the bad guys don't have access to your mobile phone too..

Here's a video from Google where they explain two step verification in greater detail:

You can also learn more about two step verification on Google's website.

By the way, note that two step verification doesn't mean that your Gmail can't ever be snooped on by remote hackers. They could, for instance, install spyware onto your computer which could monitor everything that appears on your screen. But it's certainly a good additional level of security for your Gmail account, and one which will make life much more difficult for any cybercriminal who might be targeting you.

2. Check if your Gmail messages are being forwarded without your permission

Gmail gives you the ability to forward your emails to another email address. There are situations where this might be handy, of course, but it can also be used by hackers to secretly read the messages you receive.

Go into your Gmail account settings, and select the "Forwarding and POP/IMAP" tab.

If your emails are being forwarded to another address, then you will see something like the following:

Gmail forwarding

That's fine if you authorised for your emails to be forwarded to that email address, but a bad thing if you didn't.

If your messages are not being forwarded you will see a screen more like this:

Gmail forwarding

Hackers want to break into your account not just to see what email you've received up until their break-in. Ideally, they would like to have ongoing access to your email, even if you change your password or enable two step verification. That's why it's so important to check that no-one has sneakily asked for all of your email to be forwarded to them.

3. Where is your Gmail account being accessed from?

At the bottom of each webpage on Gmail, you'll see some small print which describes your last account activity. This is available to help you spy if someone has been accessing your account at unusual times of day (for instance, when you haven't been using your computer) or from a different location.

Last account activity

Clicking on the "Details" option will take you to a webpage describing the type of access and the IP address of the computer which logged your email account. Although some of this data may appear nerdy, it can be a helpful heads-up - especially if you spot a computer from another country has been accessing your email.

IP addresses of computers accessing Gmail account

4. Choose a unique, hard-to-crack password

As we've explained before, you should never use the same username and password on multiple websites. It's like having a skeleton key which opens every door - if they grab your password in one place they can try it in many other places.

Also, you should ensure that your password is not a dictionary word, and is suitably complex that it's hard to break with a dictionary attack.

Here's a video which explains how to choose a strong password, which is easy to remember but still hard to crack:

(Enjoy this video? You can check out more on the SophosLabs YouTube channel and subscribe if you like)

Don't delay, be sensible and make your passwords more secure today

And once you've chosen a safer password - keep it safe! That means, don't share it with anyone else and be very careful that you're typing it into the real Gmail login screen, not a phishing site.

5. Secure your computer

Secure PCIt should go without saying, but this list would be unfinished without it. You need to properly secure your computer with up-to-date anti-virus software, security patches and so forth. If you don't, you're risking hackers planting malicious code on your computer which could spy upon you and, of course, your email.

You always want to be certain that your computer is in a decent state of health before you log into a sensitive online account, such as your email or bank account. That's one of the reasons why I would always be very nervous about using a computer in a cybercafe or hotel lobby. You simply don't know what state the computer is in, and who might have been using it before.

6. Why are you using Gmail anyway?

Okay, I don't really mean that. But I do mean, why are you storing sensitive information in your Gmail account?

The news headlines claim that senior US political and military officials were being targeted by the hackers. Surely if they had confidential or sensitive data they shouldn't have that in their webmail account? Shouldn't that be on secure government and military systems instead?

Always think about the data you might be putting on your web email account - because if it's only protected by a username and password that may actually be less security than your regular work email system provides.