



The Mismatch

Slack is designed as an enterprise system built for business settings. That results in a sometimes dangerous mismatch between the needs of the audience the company is aimed at serving and the needs of the important, often targeted community groups and activists who are also using it.


Two things that EFF tends to recommend for digital organizing are 1) using encryption as extensively as possible, and 2) self-hosting, so that a governmental authority has to get a warrant for your premises in order to access your information. The central thing to understand about Slack (and many other online services) is that it fulfills neither of these things. This means that if you use Slack as a central organizing tool, Slack stores and is able to read all of your communications, as well as identifying information for everyone in your workspace.

We know that for many, especially small organizations, self-hosting is not a viable option, and using strong encryption consistently is hard. Meanwhile, Slack is easy, convenient, and useful. Organizations have to balance their own risks and benefits. Regardless of your situation, it is important to understand the risks of organizing on Slack.

First, The Good News

Slack follows several best practices in standing up for users. Slack does require a warrant for content stored on its servers. Further, it promises not to voluntarily provide information to governments for surveillance purposes. Slack also promises to require the FBI to go to court to enforce gag orders issued with National Security Letters, a troubling form of subpoena. Additionally, federal law prohibits Slack from handing over content (but not metadata like membership lists) in response to civil subpoenas.

Slack also stores your data in encrypted form when it’s at rest. This method will protect against someone walking into one of the data centers Slack uses and stealing a hard drive. But Slack does not claim to encrypt that data while it is stored in memory, so it is not protected against attacks or data breaches. This is also not useful if you are worried about governments or other entities putting pressure on Slack to hand over your information.

Risks With Slack In Particular

And now the downsides. These are things that Slack could change, and EFF has called on them to do so.

Slack can turn over content to law enforcement in response to a warrant. Slack’s servers store everything you do on its platform. Since Slack can read this information on its servers—that is, since it’s not end-to-end encrypted—Slack can be forced to hand it over in response to law enforcement requests. Slack does require warrants to turn over content, and can resist warrants it considers improper or overbroad. But if Slack complies with a warrant, users’ communications are readable on Slack’s servers and available for it to turn over to law enforcement.

Slack may fail to notify users of government information requests. When the government comes knocking on a website’s door for user data, that website should, at a minimum, provide users with timely, detailed notice of the request. Slack’s policy in this regard is lacking. Although it states that it will provide advance notice to users of government demands, it allows for a broad set of exceptions to that standard. This is something that Slack could and should fix, but it refuses to even explain why it has included these loopholes

Slack content can make its way into your email inbox. Signing up for a Slack workspace also signs you up, by default, for email notifications when you are directly mentioned or receive a direct message. These email notifications can include the content of those mentions and messages. If you expect sensitive messages to stay in the Slack workspace where they were written and shared, this might be an unpleasant surprise. With these defaults in place, you have to trust not only Slack but also your email provider with your own and others’ private content.

Risks With Third-Party Platforms in General

Many of the risks that come with using Slack are also risks that come with using just about any third-party online platform. Most of these are problems with the law that we all must work on to fix together. Nevertheless, organizers must consider these risks when deciding whether Slack or any other online third-party platform is right for them.


Much of your sensitive information is not subject to a warrant requirement.  While a warrant is required for content, some of the most sensitive information held by third-party platforms—including the identities and locations of the people in a Slack workspace—is considered “non-content” and not currently protected by the warrant requirement federally and in most states. If the identities of your organization’s membership is sensitive, consider whether Slack or any other online third party is right for you. 

Companies can be legally prevented from giving users notice. While Slack and many other platforms have promised to require the FBI to justify controversial National Security Letter gags, these gags may still be enforced in many cases. In addition, many warrants and other legal process contain different kinds of gags ordered by a court, leaving companies with no ability to notify you that the government has seized your data.

Slack workspaces are subject to civil discovery. Government is not the only entity that could seek information from Slack or other third parties. Private companies and other litigants have sought, and obtained, information from hosts ranging from Google to Microsoft to Facebook and Twitter. While federal law prevents them from handing over customer content in civil discovery, it does not protect “non-content” records, such as membership identities and locations.

A group is only as trustworthy as its members. Any group environment is only as trustworthy as the people who participate in it. Group members can share and even screenshot content, so it is important to establish guidelines and expectations that all members agree on. Establishing trusted admins or moderators to facilitate these agreements can also be beneficial.

Making Slack as Secure as Possible

If using Slack is still right for you, you can take steps to harden your security settings and make your closed workspaces as private as possible.

By default, Slack retains all the messages in a workspace or channel (including direct messages) for as long as the workspace exists. The same goes for any files submitted to the workspace. If you are using a paid workspace, the lowest-hanging privacy fruit is to change a workspace’s retention settings. Workspace admins have the ability to set shorter retention periods, which can mean less content available for government requests or legal inquiries. Unfortunately, this kind of granular retention control is currently only available for paid workspaces.

Users can also address the email-leaking concern described above by minimizing email notification settings. This works best if all of the members of a group agree to do it, since email notifications can expose multiple users’ messages. 

The privacy of a Slack workspace also relies on the security of individual members’ accounts. Setting up two-factor authentication can add an extra layer of security to an account, and admins even have the option of making two-factor authentication mandatory for all the members of a workspace

However, no settings tweak can completely mitigate the concerns described above. We strongly urge Slack to step up to protect the high-risk groups that are using it along with its enterprise customers.  And all of us must stand together to push changes to the law.

Technology should stand with those who wish to make change in our world. Slack has made a great tool that can help, and it’s time for Slack to step up with its policies.

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