How secure is online shopping, really?

[This is the English version of a Norwegian article I posted February 14]

Online shopping is increasingly representing a large portion of the economy. In Norway, the size of this trade was estimated to be NOK 48 billion (USD 8.4 billion) in 2011 by DIBS (a Scandinavian payment processor) according to an article in That amount is, however, just under half of Amazon's USD 17 billion sales revenue in the 4th quarter of 2011.

When so much money is changing hands, it is important for consumers to have confidence in the security of online shopping sites.

Security in online shopping sites

The security we need to be confident about consists of several components, primarily:

  • How secure is the shopping experience itself?
  • How securely is the personal data handled?
  • How securely is the payment handled?

These components depend in part on what customers do, such as how they select passwords, then by how the shopping site is organized, e.g., its use of encryption, and, finally how the internal systems are secured.

Securing the customer's local information is the customer's own responsibility. Even though technical aids like security software and pin-code calculators can help, it is mainly education and the user's own vigilance that really help in this area.

Similarly, the shopping site is responsible for securing internal systems and the storage of private information. For an outsider, it is difficult, if not impossible, to know if the shopping site has properly secured its systems, and as a customer you have to assume they have done so. If, contrary to expectations, the shopping site has not secured their systems properly, the first indication of a problem will usually be large articles in the news about a break-in at the site. It may, however, be possible to get assistance in evaluating the security at a shopping site, if the site has been audited by an independent third party, such as the Norwegian organization Trygg E-handel ("Safe e-shopping").

There is only one security area where a customer can determine, with relative ease, how good the shopping site's security is: how the shopping site is designed and how it works while you are shopping.

Use of encryption

When you are shopping in an online store you go through several activities:

  1. Explore the shop and its selection of goods.
  2. Select the goods you want to buy.
  3. Check what is in your shopping cart.
  4. Register if you are a new customer. (Or, if you are already a customer, proceed to activity #5)
  5. Log in if you are already a customer.
  6. Go to the checkout area with your shopping cart.
  7. Enter shipping details.
  8. Pay for the goods.

My personal opinion is that all of these activities should be done over an encrypted (secure HTTPS) connection, but almost no online shopping sites have implemented this. However, it is very important that activities number 4 through 8 are always performed over an encrypted connection to prevent leaks of sensitive information.

After my December 2011 discovery of an online shop that broke several fundamental rules for good security in encrypted webpages, I have looked more closely at several groups of online shopping sites with respect to the first 6 activities above, and, in January I performed a simple survey of 34 Norwegian and 12 British online shopping sites. During this survey, I did not look into what happened when shipping and payment details are entered (activities 7 and 8), as these activities require that you are registered as a customer and complete the entire shopping process, which I was not
interested in doing as part of this survey.

The selection of shopping sites mostly included big brands in various Norwegian or British markets, most of which have brick-and-mortar stores, as well.

Each shopping site was checked for each activity point and evaluated based on whether the page a customer landed on, and all other resources (images, scripts, etc.) that were loaded as part of the page, were encrypted. If any resource, even an image, was loaded without encryption, the entire page was deemed "unencrypted". The reason for this requirement is that it requires a non-trivial effort by a user to determine why a page is marked as unencrypted by the browser. This was also done for pages where the encrypted page was "hidden" inside a frame in an unencrypted page.

The results of this survey are, to put it mildly, disappointing:

  • Just two of the Norwegian shops, Boots (which might be considered international) and Kitch'n, encrypted all activities, while none of the British shops did.
  • More than half (52%) of the Norwegian shopping sites did not use encryption at all (or not well enough) for the activities that were tested. The corresponding number for the British sites was 16%.
  • 26% of the Norwegian sites encrypted the activity for registration, login, and "go to checkout", while 67% of the British sites did the same. If we include secure display of the shopping cart, the numbers became 12% and 8%, respectively.
  • 35% had secure customer registration, compared to 75% of the British sites.
  • 26% had secure login, compared to 75% of the British sites.
  • 46% had secure start on "go to checkout", compared to 75% of the British sites. For "go to checkout", this usually means that you have to log in.
  • At one of the Norwegian and one of the British sites, these three main activities were admittedly encrypted, but they included unencrypted resources that would enable a malicious person to gain complete control of the encrypted site. Another two Norwegian sites included less dangerous unencrypted content.
  • At several of the shopping sites where encryption was not used for an activity, it was sometimes possible to activate encryption by changing the URL, but, in many of these cases, the resulting pages included unencrypted content, and, in several cases, this created vulnerabilities in the encrypted document.

Why should encryption be used?

Why should activities like customer registration, login, and "go to checkout" always be encrypted?

The answer is that these activities, at the very least, require use of your username and password, and may also ask for other private details such as address and phone number, or provide access to them, and sometimes information about your social security number may be involved, too. In many cases, the shopping site will also store information about your credit card in your profile, meaning that you don't have to type it every time you're shopping. In such cases, should malicious persons get hold of your password, they can go shopping with your credit card.

When something is sent unencrypted, anyone who is in control of a network router between you and the shopping site, such as in a wireless network, would not only be able to listen in on what is being transmitted, but would also be able to easily change the content being transmitted, which could include adding code that sends a copy of whatever is entered on the page to the attacker.

One possible way such an attack can be carried out is that somebody places a "Free Wi-Fi" network in travel hub (e.g., a railway station, bus station, or airport) where many people will sit down to use their mobile phones or PCs. With the right software installed in the network, it is very easy to listen in, or even modify, the unencrypted traffic crossing the network.

On three of the Norwegian sites, and two of the British ones, the usernames and passwords that were entered on unencrypted login-pages were admittedly sent encrypted, but this only provides an illusion of security, since an attacker can easily change the content of the unencrypted page so that a copy of the information is sent to a different destination in addition to the real login to the shopping site. It is worth noting that Eric Lawrence of Microsoft called this "Critical Mistake #1" in an IEBlog article back in 2005. It is rather incredible that we are still, in 2012, seeing this kind of login page being used.

For another of the shopping sites, several activities were encrypted, but this was hidden away inside a frame that was hosted on an unencrypted site. Also, the allegedly-secure page inside the frame, where you might be asked for your social security number, turned out to be violating most rules about how secure pages should be constructed and opened multiple security vulnerabilities. Effectively, the activity was done over an unencrypted connection, as it is not trivial to discover that encryption was used in the frame or that it suffered from several vulnerabilities, and an attacker can easily change what is actually loaded in the frame, since the instructions are sent unencrypted. Such replacements cannot be discovered easily. This is another example of web design that should simply not be used by a serious shopping site in 2012.

It is, however, not just use of encryption that determines if the connection to the shopping site is secure. As part of this survey, I also checked the patch status for a less visible vulnerability that I have discussed many times before, mostly on the Security Group home page: the "Renego" issue, which was discovered and patched over two years ago. I discovered that only 29% of the Norwegian shopping sites had upgraded their servers to patch this problem, while 67% of the British sites had done so (the general patch rate is now 65%). In all, 53% of the unpatched Norwegian sites were also configured in such a fashion so that they were vulnerable to a full "Renego" attack, allowing an attacker to inject commands to the website and have them executed with the user's credentials.

What can be done to improve the situation? First, the shopping sites must fix their sites, but, in the long run, we need good control routines, such as by certification services, as well as customers learning to keep an eye on their own security.

Certification services

As mentioned above, it is usually difficult for outsiders to determine how good the security of a shopping site really is. This is due to the fact that, to be able to do that, we need access to information that companies for business reasons seldom make available. It is, however, possible that an independent and trusted third party might be allowed to audit the company and its compliance with specific requirements, issuing a certificate or seal if the requirements are met.

In my opinion, such requirements should include a requirement about using encryption for all functionality that handles sensitive information.

In Norway, the organization Trygg E-handel is such a certification service. Among its requirements for online shopping sites, it states that "Personal information must be protected against external access" (my translation), which, in my opinion, requires that all handling of such information must be encrypted, as you cannot protect a system against "external access" if the unencrypted password is easily available on the net. Still, two of the four shopping sites in my survey that were certified by Trygg E-handel did not use encryption for login and registration.

What can the customer do to ensure that a shopping site uses good encryption?

Primarily, customers must make themselves familiar with how their browsers indicate that a webpage is encrypted. This indication appears with slightly different designs and locations across the various browsers, and the indication can also change, depending on which kind of SSL certificate the server presents to the browser. It is, however, frequently associated with an image of a padlock, such as in Opera and Internet Explorer, but not always; Firefox is currently using a slightly different presentation. In addition, most browsers show a different, green variant of the padlock when the secure site is using an Extended Validation (EV) certificate for which the information has been extensively checked. Such certificates are frequently used by online banks and should be used by any site that charges payment for goods and services.

The following picture shows examples of how an unencrypted site, an encrypted site, and a site using an Extended Validation certificate are presented in various browsers:

When customers visit an online shopping site, they must check the padlock before starting to enter usernames, passwords, and other personal information, such as during registration or before starting the payment process. If the padlock (for either normal encryption or Extended Validation) is not displayed, you should not continue the transaction, but instead leave the site, as the information is not handled securely enough. You should also inform the shopping site about what you observed.


Based on the above, I would say that the lack of encryption, and lack of timely server upgrades to fix well known security problems, clearly indicate that Norwegian shopping sites are not secure enough.

The question is what these findings indicate about the security of shopping sites in other countries? Given the numbers for the British sites mentioned above, as well as the findings in my e-bookstore survey in December of about 50% of surveyed shops using good encryption, (which may be too few datapoints to be really significant), there is at least a good indication that there is still a lot of room for security improvements in the online shopping industry.

At the very least, based on the single certification service I reviewed, I would say that these services still have room for some improvement in the security area.

Not using encryption for sensitive information sends a signal to customers that a business has not given sufficient attention to the security of its shopping site. This signal is, I would hope, mistaken, but I am afraid that it can create a justified doubt about how well the shopping site's internal security is handled. Or, to put it another way: It is a very good practice to lock the back door to your house, but that won't help you if the front door is wide open.

I urge online shopping sites to take security and the use of encryption seriously. If a shopping site is not using encryption for sensitive information, this should be fixed as quickly as possible, and, if repairs cannot be completed within a short time, then the site should, strictly speaking, be taken offline until the problem has been fixed.

It is a sad thing to say, but, unfortunately, I doubt that there will be any significant improvement until somebody completes an attack (as happened to the social websites with the Firesheep utility), or until customers become more observant and vote by moving their mouse clicks to online shopping sites that guard their customers' security better.

2 thoughts on “How secure is online shopping, really?”

  1. MD5 is not an encryption function, it is a one-way function; meaning that it is supposed to be easy to calculate foo = MD5(bar), but bar=inverse-MD5(foo) should not be easier than attempting every possible combination of the input. (In an encryption function it is possible to do both operations easiliy if you know the encryption key)The main uses for a one-way function in crypto is to calculate checksums of content and pseudo-random numbers, as varying one bit of the input is likely to create a wildly different result, and it is highly unlikely that two different inputs will produce the same result. At present, MD5 is creaking in the seams, and it has become easier to do some of the operations that was supposed to be hard, but the function is not yet broken (and definitely not close to the extent that MD2 is). For that reason it is no longer considered safe to issue new certificates signed with MD5, but due to other security measures it is still reasonably safe for use in SSL/TLS, although it is time to start phasing that usage out by migrating to TLS 1.2.

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