Slack Security Best Practices: Protect Your Workplace Conversations

Slack has become the digital office for millions of teams. But with convenience comes risk — sensitive company data, client information, and personal details flow through Slack channels every day. One misconfigured setting or careless message can expose your organization to real threats.

Here's how to lock down your Slack workspace without killing productivity.

DMs vs Channels: Understanding the Security Difference

Most people assume Slack DMs are private. They're not — at least, not completely.

Feature	DMs	Channels
Visible to workspace admins?	Yes (on paid plans with compliance export)	Yes
Searchable by others?	No	Public channels: Yes
Retained after someone leaves?	Yes	Yes
Can be exported?	Enterprise Grid: Yes	Yes (all plans)

Key takeaway: Treat every Slack message — DM or channel — as potentially readable by your employer. If you wouldn't say it in a company email, don't say it in Slack.

The Hidden Risks of External Sharing

Slack Connect lets you collaborate with people outside your organization. It's useful, but it creates several security blind spots:

1. Shared Channels With Vendors

External partners in a shared channel can see message history, uploaded files, and pinned documents. If someone shares a sensitive internal document in the wrong channel, external parties see it instantly.

2. File Sharing Without Expiration

Files uploaded to Slack don't expire by default. That contract PDF you shared six months ago? Still downloadable by anyone in the channel — including people who joined after it was posted.

3. Guest Account Sprawl

Single-channel and multi-channel guests accumulate over time. That contractor from 2024 might still have access to your workspace.

Fix it: Schedule quarterly audits of external members and guest accounts. Remove anyone who no longer needs access.

Setting Up Two-Factor Authentication (2FA)

If your workspace doesn't enforce 2FA, you're one phished password away from a breach.

How to Enable 2FA on Slack

1. Go to your profile → Account settings
2. Click Two-factor authentication → Set up two-factor authentication
3. Choose your method: authenticator app (recommended) or SMS
4. Save the backup codes in a secure location

For Workspace Admins: Enforce 2FA

Navigate to Settings & Administration → Workspace settings → Authentication and require 2FA for all members. No exceptions.

Pro tip: Store your Slack 2FA backup codes in a password-protected memo on LOCK.PUB. Far safer than a screenshot sitting in your camera roll.

Essential Admin Controls

If you're a Slack admin, these settings should be configured on day one:

Setting	Recommended	Why
Message retention	Custom (90 days for general, longer for compliance)	Limits exposure if breached
File sharing to external	Restricted	Prevents accidental data leaks
App installation	Admin approval required	Blocks rogue integrations
Email display	Hidden from external users	Reduces phishing targets
Channel creation	Open for internal, restricted for Slack Connect	Controls information sprawl
Session duration	30 days max	Forces re-authentication

Managing App Permissions

Third-party Slack apps are a major attack vector. Every bot or integration you install gets some level of access to your workspace data.

• Audit existing apps quarterly
• Remove unused integrations immediately
• Require admin approval for new app installations
• Check OAuth scopes — does that simple poll app really need to read all messages?

What You Should Never Share in Slack

This isn't about paranoia — it's about common sense. These things should never appear in a Slack message:

• Passwords or API keys — Use a password manager or secrets vault instead
• Credit card numbers — Not even partial numbers
• Social Security or government ID numbers — Always share through encrypted channels
• Unencrypted customer data — Especially if you're bound by GDPR, HIPAA, or SOC 2
• Internal salary or HR information — Use official HR systems
• Legal documents or attorney-client communications — These lose privilege protections in Slack

A Better Way to Share Sensitive Information

Instead of pasting credentials directly into Slack, use a password-protected link. Create one on LOCK.PUB — it works like this:

1. Write the sensitive information in a secure memo
2. Set a password
3. Share the LOCK.PUB link in Slack
4. Send the password through a different channel (text message, phone call)

The information is encrypted and accessible only with the password. Far safer than a plaintext Slack message sitting in searchable history forever.

Slack Security Checklist for Teams

Run through this checklist quarterly:

• All members have 2FA enabled
• Guest and external accounts audited and pruned
• App permissions reviewed and unnecessary integrations removed
• Message retention policies configured appropriately
• File sharing restrictions set for sensitive channels
• Team trained on what not to share in Slack
• SSO configured (Enterprise plans)
• Data Loss Prevention (DLP) tools evaluated

What to Do If Your Slack Account Is Compromised

1. Change your password immediately and revoke all active sessions
2. Notify your workspace admin — they can force-logout all devices
3. Check connected apps — revoke any unfamiliar OAuth tokens
4. Review recent messages — look for anything sent from your account that you didn't write
5. Enable 2FA if you haven't already

Wrapping Up

Slack is built for speed, not secrecy. The default settings prioritize collaboration over security, which means it's on you and your admin team to close the gaps. Take 15 minutes today to review your workspace settings, enable 2FA, and establish clear guidelines for what should and shouldn't be shared in Slack.

For any sensitive information that absolutely needs to be communicated to a colleague, skip Slack entirely and use a password-protected link instead.

Create a secure password-protected link on LOCK.PUB →