Enhancing the security of your DTM implementation

We are all aware of the importance of creating secure products. In a previous post, I explained how to set up a workflow for a DTM implementation. One of the consequences of using this workflow is that only a reduced number of users can cause damage to the website via DTM. This is also good from the security perspective, as it reduces the risks of a successful attack. This is probably enough for most companies.

Financial institutions and DTM

Having said that, we must also realise that it is virtually impossible to create a completely invulnerable software product and DTM is not an exception. Banks and similar companies take the security to the next level. For them, the minimum security level should be “paranoid”. For obvious reasons, this paranoid level of security also applies to DTM. If an attacker gained access to DTM, he could very easily inject malicious JavaScript code to the whole website, by just adding a page load rule.

There are many places in DTM where an attack could take place; this is what is called the attack surface:

  • Use brute force to get to the password of one of the publishers or administrators.
  • Find a vulnerability in the DTM UI and gain control of an account.
  • Find a vulnerability in Akamai (current provider for DTM) and gain control of the servers.

I am not implying that DTM is insecure; I am 100% sure that the developers take security very seriously, but we must never forget that there can always be a hidden security hole.

Self-host DTM library

The immediate solution to reduce the attack surface is to self-host the DTM library. You would just use the DTM UI to create the rules and, once the development is finished, download the DTM JavaScript library. You can then run an audit of the files and host them in your own servers, which you have already hardened. With this approach, all three security concerns raised in the previous paragraph are gone. Even if an attacker gained access to the DTM, he could not modify the DTM library in your production servers.

In order to do this, you first need to enable the “Library download” option, under the “Embed” tab.

DTM library download enabled

After configuring the options, you get a URL to download both the staging and production libraries:librarydownload-2

Remember to update the links to the library in the HTML, as specified in the “Header code” section:


DTM library workflow

The previous solution works, but it adds a level of complexity for the DTM users. When debugging unpublished rules, the DTM Switch is completely useless, as it only works if the library is hosted in Akamai. You need to use tools like Charles, which make the whole process more complicated: you might need a license, you will need to download the library with every rule change, you need to learn how to manually replace the live DTM files with your local version… One problem has been solved, but a new one has been created. In particular, non-technical people will find quite challenging this solution.

My proposal in this case is to use a hybrid solution:

  • Use Akamai for the development environment
  • Use self-hosting for the test and production environments

and a create new workflow:

  1. The report suites in DTM should always point to development and/or UAT values.
  2. Your friendly marketer should have access to a development server with a working version of the website, where DTM is loaded from Akamai URLs, as with the typical DTM deployment. In this environment, she can easily create and test new rules using the DTM Switch. She should only have user permissions in DTM. Any successful attack on DTM will be confined to the development environment.
  3. Once the rules have been finished, a tester should verify the correctness of them. If everything is correct, the tester should approve and publish the rules. This is different from the workflow I suggested in a previous post: now, the tester has both approve and publish privileges.
  4. An automated script should download regularly the production DTM library and deploy the JavaScript files in the SIT/UAT/staging environments.
  5. Security audits should regularly be made to these JavaScript files.
  6. When pushing the whole development environment to SIT/UAT/staging, another script or process should automatically modify the DTM links in the HTML, to point to the correct server (not Akamai). These links are those in the “Library Download” tab.
  7. Website testers should only see the approved and published rules and report any errors.
  8. In pre-production, the report suite ID of the DTM library should automatically be replaced with the production RSID.
  9. The production environment should be exactly the same as pre-production.

It is a complicated solution, but it combines both the easiness of the DTM Switch for development and the security of self-hosting.

On final note. You will have noticed that the SIT/UAT/staging environment will have a slightly different version of the DTM library, than pre-production and production, as the RSID will be different. I would also expect that server names will be different. In this case, one solution is to replace the URLs in DTM with placeholders:


Your scripts I mention should also do a find and replace in the JavaScript files, looking for these placeholders and replacing them with the correct URL.

DTM, products and W3C data layer

Before getting into the details of the post… Happy New Year to all of you! I hope that 2016 is full of DMPs, DTMs and Analytics 🙂

Now, going back to today’s topic, I want to talk about how to create the products string in DTM using the W3C data layer. One of the reasons why we prefer a tag management solution (TMS) over hard-coded snippets is to write less code. All modern TMSs include features to set analytics variables using a point and click interface, usually through Web. In the case of DTM, you can create a data element that reads a data layer variable; you can then assign it to an eVar or a prop, without writing a single line of code.

However, when it comes to the products string, things are not that easy. There is no simple way of creating a one-size-fits-all solution for this variable. Let’s have a quick reminder of this variable’s structure:

which can be repeated as many times as needed, once for each product, using the comma as separator. Each element in this structure has its own rules:

  • Category. It is rarely used, as there was a limitation in SiteCatalyst v14 that only allowed one category per product. This limitation was lifted with v15, but very few implementations use it anyway.
  • Product. This is the only mandatory element.
  • Quantity. Only on the order confirmation page.
  • Price. Total price of all units combined for that product; only on the order confirmation page.
  • Product-specific events. Optional.
  • Merchandising eVars. Optional and, usually, only on product view or add to basket.

Data Elements for products

As it can be seen, there are many potential combinations of these elements. As a consequence, my recommendation is to create one data element (custom script) in DTM for each of the cases. For example:

  • Product listing page (PLP)
  • Product description page (PDP)
  • Cart page
  • Add to basket
  • Remove from basket
  • Order confirmation page


As an example, on the order confirmation page, you could use code similar to the following:

In this example, if a product is a gift, event48 should also be set.

Remember to use the correct data layer object for each case:

  • digitalData.product: PDPs and PLPs
  • digitalData.cart: add to basket event, cart and checkout pages
  • digitalData.transaction: order confirmation page

I have already described some details about digitalData.product and digitalData.cart in my post The W3C data layer – part II.

Products in rules

As you know, the recommended approach to set Adobe Analytics variables using data elements and is to use directly the UI:


However, the products string and the purchaseID variable cannot be set through the UI. The only option is to set them in code, using something similar to:

Please note that the events string must also be updated depending on the product-specific events. Following the previous example, event48 needs to be set only if it is set in the products string. In rules where the Adobe Analytics call is s.tl() , DTM will detect that s.products  has been set and will add it to s.linkTrackVars , but not the events in it. Thus, the variable s.linkTrackEvents  must also be updated. For example:

Be careful if you use “eventX” without the equals sign (=) in the call to indexOf() , as there is the small risk of setting the wrong event. For example, s.products.indexOf("event12") will detect event12, but also event120event129.

When to use and when NOT to use DTM

A while ago, a customer requested a call with me to discuss one issue. Usually, I get more technical questions, but this time, he wanted to have my input regarding something completely different. The developers had realised that they forgot to include a JavaScript library in the website and they could not add it immediately, due to code freeze. They thought of an alternative solution: load it through DTM. My customer, from the marketing department, was not sure whether this was possible or acceptable and, therefore, wanted to know my point of view.

I must admit that, initially, I was a bit perplexed and did not know exactly what to reply. This was the first time I received this question and I had never thought about it. However, I quickly came with a proper answer and this is what I suggested. It must be noted that this is my personal perspective, not Adobe’s.

In order to reply to this question, you must first think about governance. Who manages DTM? Who owns DTM in the company? What is the purpose of using DTM? I think that DTM is a marketing tool, managed by the marketing department, used to deploy marketing tags in a website. So, if the new piece of code that needs to be added to DTM is requested by the marketing department, then it will probably make sense to use DTM; on the other hand, if it is the IT department requesting the addition, I would recommend against using DTM for it.

Technically, it is possible to deliver any JavaScript (and even HTML) through DTM. However, the fact that it is possible does not mean that it should be done. Think about the following questions when adding a piece of JavaScript that was not requested by the marketing department: who owns that piece of code? who updates it? who fixes it if stops working? who is to blame if it is inadvertently removed? what happens if DTM is removed? The marketing team will not want to take any responsibility of code they do not even understand.

So, to summarise, from my point of view, here you have some cases that are suitable for DTM and cases that are not:

  • In DTM:
    • Web Analytics tags (like Adobe Analytics)
    • Optimisation code (for Adobe Target, for example)
    • DMP tags (AAM also has a module in DTM)
    • Third party re-marketing tags
    • On-site surveys
  • Not recommended in DTM:
    • Generic JavaScript libraries (for example: jQuery)
    • Website functionalities (chats, UI effects)
    • Code that needs to be executed in a very specific location of the page (i.e. not at the top or the bottom)
    • CMS libraries

Can you think of any other case that would fit in one or the other case? If so, please, leave a comment!

Executing DTM at the top of the page

If you have been developing websites for a while, you will know that one of the typical recommendation is to execute as much JavaScript as possible at the bottom of the page. This is nothing new and Yahoo recommended it in 2007. The reason is very simple: JavaScript code tends to add a delay, both when loading the JS file and executing it; so, moving it towards the bottom, you make sure the HTML is loaded and the page is rendered before starting to execute any JavaScript. The user believes the page is loaded a bit sooner than when it is actually fully loaded. DTM knows that very well and this is why you have to add the two pieces of code: one at the top and one at the bottom of the HTML.

This approach works very well in most cases. DTM loads first the code that needs to be at the top of the page, but then allows you to defer the rest of the loading and executing at the bottom of the page, like Adobe Analytics, Adobe Audience Manager and 3rd party tags. This is the typical recommendation. The risk of this recommendation is that some page views might be lost, if the user moves away too fast.

However, there is one particular case where this recommendation fails very often. I was working with a well known British newspaper, helping them with the migration from another Web analytics tool to Adobe Analytics. They wanted to run both tools, side by side, for a short period of time, to make sure the numbers did not change too much. To our dismay, Adobe Analytics was showing a much lower number of page views than the other Web analytics tool. We realised that the problem was that Adobe Analytics was executed at the bottom of the page, as per the typical recommendations. The homepage of newspapers tends to be massive, taking many seconds, even minutes, to fully load. This means that the code at the bottom has the risk of not being executed, if the user clicks on a link or closes the browser tab after quickly reading the headlines.

The only solution in this case is to reorganise the code in a slightly different way:

  • The DTM header code needs to be moved to the bottom of the <head> section, ignoring the recommendation in DTM of pushing it to the top.
  • The DTM footer code should still be at the bottom of the <body>  section.
  • Add the data layer before the DTM header code.
  • Configure the Adobe Analytics tool to be executed at the top of the page.
  • Set all Page Load Rules that will be setting analytics variables to be executed at the top of the page.
  • The Data Elements used for Adobe Analytics cannot use CSS selectors.

This solution guarantees that the analytics code is executed most of the times, at the expense of delaying for a few hundred milliseconds the load of the page.

DTM permissions and workflow

Some time ago, I received an urgent call from a customer that claimed that DTM broke their website. They wanted to see me immediately, as that was causing a huge impact in them. Fortunately, the problems only manifested in staging, but they could not move to production. Once I arrived at my client’s office, I immediately realised what had happened: the data analyst had created some data elements using JavaScript he found on the Internet and he just copied and pasted the code. The code worked on his computer, so he went to approve and publish it. The reality was that his code only worked in IE and crashed in other browsers.

As I have already explained, there are many benefits from using a tag management solution. However, with great power, comes great responsibility. Using DTM does not mean that marketers can implement anything they want and publish rules as they like. To the contrary, they must be very strict. The previous example is exactly the opposite of what must be done.

The solution I suggested to my client is to follow a very strict workflow and use wisely the permissions:

  • Anybody who needs to create new rules should be given the User role. This allows the user to create new rules and make sure they work fine using the right DTM plugin.
  • You need to have a group of testers that have the Approver role. They are responsible of making sure the new rules not only work fine in one browser, but they are cross-browser compatible, do not break the website, capture the expected data…
  • Once the rules have been approved, it is time to publish them. Very few people should have the Publisher role and publishing rules should be done very carefully, just like a typical code release.


Some additional recommendations:

  • Publish rules at a certain time every week, so that, in case something goes wrong, it is easy to identify that the new rules are the culprit and roll back to the previous approved version.
  • Get some developer’s time in order to create JavaScript rules. He will probably need 5 minutes per rule and will do it right the first time.
  • The testers, ideally, should be the same as the website testers, so that the tests are full tests, with the right tools and environment.

Custom conditions in DTM

When creating both page load rules and event based rules in DTM, you have the option of configuring some conditions to determine when to fire those rules: parts of the URL, cookies, browser properties, JavaScript variables… If you add more than one condition, the AND boolean operator is applied to all conditions. However, in some cases, these out-of-the-box conditions are not enough. Thankfully, DTM offers the custom condition, where you can write pure JavaScript.

The first thing to note is that the snippet of code must return a boolean. It might work with expressions that can be evaluated as true/false (like empty/non-empty string, 0 or different than 0), but I have just not tried them. In other words, there must be a return statement within the code. In fact, the return statement must be at the very end of the code.

This code will NOT work:


What I always do in this situation, is create a variable named ret and return it at the very end.


Execute JavaScript in event based rules

If you create an event based rule that is fired upon click of a link and you want to execute some JavaScript, chances are that, if you add it to the “JavaScript/Third Party Tags”, it will never be executed. The reason is that the browser has already been instructed to unload the page and move to a new URL. It will not have time to load an external JavaScript and executed; if fact, I think that it will not even attempt to do it.

What can you do in this case? Use the custom condition of the rule, to make sure the JavaScript is executed. For example, to write a cookie:


There is no need to return true in this case. However, it is more convenient to leave it as shown, as the console will then show the rule as executed.

Capture information from the clicked element

Imagine you have an event based rule in which you want to capture the full URL of the clicked linked and store it in prop1. Your first idea would be to create a data element that returns this.href:


However, one limitation of data elements is that they have no idea of what DOM element has been clicked, if any. If you try to use the this keyword in data elements, you will get a surprise: it will not work as expected.

One possible solution is to go to the custom code of the Analytics section as set the value there:


Remember to include s.linkTrackVars if you are making an s.tl() call.

I do not like the previous approach, as it is not elegant and you need to explicitly open the editor to see the contents of the rule. My preferred solution is to use the custom condition and set a data element on the fly; then, in the analytics section, just reference the data element as usual:




Do you have any other uses for the custom conditions in DTM? I would love to hear your opinions on that.

Use a tag manager

Back in the old days, the only way to add Web analytics code to a website, was through manual coding. If you were using Adobe Analytics, you would need to add two pieces of code into the website: the s_code and the on-page code. The s_code is a JavaScript file with common code for Adobe Analytics (SiteCatalyst) and the on-page code contains the page-specific data. I am sure many of you are familiar with these lines of code:

While this does not seem to be a great problem, my experience with many customers shows that this traditional solution is far from ideal. Typical issues that I have found are:

  • Web developers have usually little or no knowledge of Adobe Analytics code. The moment you mention “eVar” or “prop”, they completely disconnect from the conversation until they clearly understand what these words mean. Do not get me wrong, I have been a developer myself, I have nothing against developers, but I know that it is very difficult to find a web developer that understands Adobe Analytics.
  • Changes take a very long time to be published. Even the minimum code change (just adding an eVar, for example), can take weeks, if not months, before it is live. The main reason is that, any new feature must be added to a scrum backlog, a change request…
  • Disconnect between IT and marketing. These two departments tend to have very different goals. As a consequence, what is of great importance for a web analyst, might be considered low priority by the scrum master.

If you search for more reasons, you will find many more.

So, what is the solution? Use a tag management solution, like Adobe Dynamic Tag Management. This is not the silver bullet that will solve all your problems, but it will help move forward more easily. Do not even think on developing your own solution: it will take you years before you have a solution that matches the worst commercial solution.