Don’t Slack on Slack: The Challenge of Unstructured Collaboration Data in Enterprise Ediscovery

| April 24 2019

Every time we turn around, more people are using the collaboration platform Slack. As of January 2019, Slack announced that it had surpassed 10 million daily active users, including 65 companies in the Fortune 100. While the free version is still the most popular, more than 85,000 individuals and organizations pay to use upgraded versions. And these daily users aren’t just using Slack a little: surveys have shown that users have Slack open for more than 10 hours each weekday. The upshot is that work communications that used to happen on email now increasingly happen on Slack.


This is great news for communication and collaboration—the reasons Slack was created in the first place—but less-great news for ediscovery and legal compliance. If conversations about work are now on Slack, how are organizations capturing, preserving, and producing those messages for use in litigation?

The answer, for many, is that they’re not. That’s partly because Slack’s growth rate has been faster than most companies can keep up with, but it’s also due to some serious challenges with managing the unstructured data in Slack for use in ediscovery. Those challenges range from the existential—issues wrought by the very nature of Slack—to the technical. As with most problems, the first step to solving them is understanding them, so let’s take a closer look.  

Existential Challenges: Slack’s Design Defies Traditional Ediscovery

Before we even address the issues created by Slack’s design, there’s one small preliminary problem. To try to do ediscovery with Slack, you have to know (or at least suspect) that your organization is using it. Otherwise, you’ll never go looking for it, and your ediscovery will be entirely Slack-deficient. While your policies might prohibit downloading or using apps without approval from IT, we’re sorry to tell you that people don’t always—gasp!—comply perfectly with company policies. There are no barriers to starting Slack use: the free version is readily available and can be downloaded and set up in just moments. Don’t assume that no one is using Slack at your organization without at least investigating.

If you do find that you’re using Slack, remember that it was never designed as an ediscovery tool (if it had been, we’re betting its growth would have been somewhat more modest). Its raison d'être is improved and expedited communication and the collaboration it allows. But, no matter how good Slack may be at its intended purpose, that doesn’t make it exempt from the constraints of standard business, including responsible information governance and legal compliance. In short, if anyone in your organization is using Slack for work (and it takes at least two to tango), you need to evaluate those messages for discoverable information just as you would evaluate emails, text messages, and other forms of business communication, and you need to preserve potentially discoverable information.

Herein lie the two biggest ediscovery challenges within Slack: determining custodians and defining the scope of a hold or a search.

With emails or text messages, it’s easy to establish who’s a custodian for what message. If you sent it or received it, voila, you’re a custodian, and your entire email account can be placed on a legal hold. Then, once you’ve defined the scope of a discovery search—perhaps with custodians, date limits, and a few keywords—you can search through that custodian’s messages for potentially responsive information.


But Slack is not an email inbox. It is, in effect, an unstructured digital bulletin board or a ticker tape. Within a given channel or message history, Slack messages unfold chronologically, without any indication of who’s read (or even scrolled past) what messages. A “custodian” for a Slack message, then, could be anyone who belongs to the channel in which that message appears—meaning you have to place a legal hold on the entire channel.

When it comes to defining scope more granularly, the chronological nature of Slack feeds presents another problem: conversations unfold slowly, over the space of many messages, often interrupted by irrelevant messages. Instead of self-contained emails that present a single conversation in a somewhat-organized fashion, unstructured Slack conversations need to be read in their full context—often spanning multiple screens—to be truly understood. That means you can’t just preserve or produce those individual messages that contain keywords; you need to also capture everything around them so that they make sense.

Okay, so you have to determine whether you’re using Slack, rethink your definition of custodians, and expand the way you scope discovery. Then you’re good to go, right? Sorry, still no.

Technical Challenges: Slack Isn’t an Ediscovery Tool

Slack has recognized that organizations need a way to preserve messages, but because it’s not designed for ediscovery, the tools that it’s introduced are blunt instruments at best. Those tools are lacking in part because they attempt to resolve both information governance challenges (the need to defensibly delete outdated information) and ediscovery challenges (the need to preserve potentially relevant and discoverable information) in one fell swoop.

Case in point: Slack has introduced functions that allow organizations to set a message retention period, after which messages are automatically deleted. It’s also added the ability to put an entire channel on legal hold, so that messages in that channel aren’t deleted, preventing spoliation. (Note that if you’re using the free version of Slack, you’ve only got access to the most recent 10,000 messages anyway—so anything older is not readily available to you.)


Slack’s legal hold function, though, is entirely binary. It’s either on or off, with no ability to specify particular dates. This is probably fine if you only have one litigation matter or one legal hold at a time. But if you’re in a more typical organization, where you at least sometimes have overlapping legal holds for different custodians, you’ll quickly find that you can’t release the first hold without losing information that might be discoverable under the second. That means that once you start implementing holds, you may find that they’re effectively permanent. In other words, you’ll either release legal holds and potentially spoliate messages in the process, or you’ll maintain those holds and thereby retain messages for much longer than you otherwise would.

There’s an obvious solution here: export data that you need to save outside of Slack and continue deleting messages in Slack according to your records retention policy. Boom, you’re done—right?

Yes—but exporting Slack data in a useable format is a lot harder than you’d think. Slack’s only export tool uses a JSON file type, which is unwieldy at best. Each day of activity in each channel creates a separate JSON file—so if you’re tracking a conversation that spans multiple days, you’ll have to toggle between different files to review it or make any sense of it. And you know what you don’t need in ediscovery review? Something that’s going to slow the process down or make it even more expensive.

Then there’s also another problem that could probably fit under either of these broad categories: the enormous use of Slack, combined with its ability to integrate with other apps and its ability to incorporate links and files of all types, means that there are simply massive amounts of complex and varied data within Slack. As with all types of ediscovery, the more data, the harder the task.

Finally, we mentioned this in passing a moment ago, but it’s worth bringing up again: if you’re going to use Slack at your organization, you need to ensure that you’re using the right version. The free version doesn’t allow any preservation of messages, so that’s not an option. While the premium version allows some increased capabilities, those tools obviously fall short of what’s needed for most organizations. If you have any complex litigation or ediscovery needs, your best bet is to choose Slack Enterprise Grid, which is optimized for ediscovery support.

Hold on, though—didn’t we just say that Slack’s ediscovery tools aren’t sufficient? Why do you need Enterprise Grid if it won’t provide you with a comprehensive ediscovery solution?

Because Enterprise Grid gives you access to Slack’s discovery application programming interface (API), and that’s what enables Slack to work with a dedicated ediscovery tool that does solve these challenges.  

Like what? We’re glad you asked.

Hanzo Hold Overcomes the Challenges of Ediscovery in Slack

Realizing that all of these problems existed was what led us to create a solution: Hanzo Hold. It allows users to capture potentially responsive messages in a protected external repository associated with a particular hold. Each individual legal hold can be implemented and released as needed without disrupting the archives associated with other holds. And Hanzo Hold doesn’t care how big your archive is or how many associated files or file types are embedded. Best of all, the archives created by Hanzo Hold can be reviewed naturally, in the order that messages were written in a channel, without shuffling between different files or trying to line up which conversation is which. That saves time—and money—in review while ensuring that you can see every part of a message’s history.


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Slack is revolutionizing the workplace, but it shouldn’t be destroying your legal compliance in the process. Don’t slack off on figuring out how to manage ediscovery of Slack messages. Start a conversation with Hanzo today and learn what it means to capture confidence.

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