With over 45 million daily users, Slack has established itself as one of the most widely used apps for workplace communication and collaboration. Given the volume and sensitivity of data that flows through the app daily, one can’t help but wonder whether Slack provides sufficient security to keep it safe.
So, is Slack encrypted, and what type of security features does it offer? In this guide, we’ll provide a detailed overview of the app’s security stack and explain the encryption it offers, so you can decide whether you're comfortable using it for sensitive communication.
Slack Encryption: How Does It Work?
Slack offers encryption as one of its key security features. The app encrypts data in transit (data that’s actively moving between devices, networks, and systems) and data at rest (data that’s not actively moving):
- Data in transit: Slack leverages TLS 1.2 protocols, AES2456 encryption, and SHA-2 signatures to keep information between clients and the service secure.
- Data at rest: Slack relies on FIPS 140-2-compliant encryption standards for protecting all data at rest, including relational databases, database backups, and file stores. It stores encryption keys on a secure server on a separate network with limited access.
According to Slack’s security whitepaper, the company has measures in place to protect the creation, storage, retrieval, and destruction of encryption keys and service account credentials, helping safeguard user privacy and security.
Is Slack End-to-End Encrypted?
While Slack uses robust encryption to protect data in transit and at rest, it doesn’t provide end-to-end encryption (E2EE), which is widely regarded as the industry standard. Although an unlikely scenario, the lack of E2EE could potentially mean that third parties, such as Slack’s employees, law enforcement, or malicious actors, could gain access to the app’s messages.
Despite the lack of E2EE, Slack states that its encryption practices still provide a high level of security. The platform:
- Hosts each customer’s data in a shared infrastructure with logical separation between tenants
- Relies on a combination of storage technologies to keep customer data safe from hardware failures
The entire Slack service is hosted in data centers operated by leading service providers, enabling state-of-the-art protection against threats.
What Other Slack Security Features Protect Your Data?
Besides strong encryption, Slack implements a range of security options and best practices for data protection and safe communication across areas such as:
- Network security and server hardening
- Endpoint security
- Access control
- Data retention and disposal
- Disaster recovery
- External audits and validation
1. Network Security and Server Hardening
To provide a high level of data protection, Slack divides its systems into different networks. For example, there’s a clear distinction between the following:
- Systems supporting testing and development activities
- Systems supporting the app’s production infrastructure
These are separated to prevent unauthorized access and offer testing flexibility without jeopardizing production. All servers within the production environment are hardened to close vulnerabilities and reduce the risk of attacks. In Slack’s case, this means implementing practices such as disabling unnecessary ports and removing default passwords.
To further protect the production environment, Slack applies restricted network access; only a small number of production servers are accessible via the internet, with special protection against distributed denial-of-service (DDoS) attacks and host-based intrusion.
2. Endpoint Security
Slack pays special attention to endpoint security, ensuring all workstations are properly:
- Configured
- Updated
- Tracked
- Monitored
Endpoint security involves enabling data encryption at rest, setting up strong passwords, and locking workstations when idle. It also includes constant monitoring for vulnerabilities such as malware and unauthorized access.
All mobile devices that connect to Slack are enrolled in a special management system to ensure compliance with security standards.
3. Access Control
When it comes to access control, Slack focuses on three aspects:
- Provisioning: Slack’s employees can only access the data they need to perform their job. The app reviews its role-based permissions at least once every quarter.
- Authentication: Access to Slack’s systems containing confidential or sensitive information is granted only through multi-factor authentication (MFA) to minimize the risk of intrusions. Whenever possible, Slack uses private authentication keys alongside MFA for additional security.
- Password management: Employees must use an approved password manager when accessing Slack to reduce the risk of phishing, password reuse, and credential leak.
4. Data Retention and Disposal
To protect your information and minimize the risk of third parties accessing the data, Slack implements strict data retention and disposal policies.
All customer data is removed immediately after the end user deletes it or when the message retention configured by the customer administrator expires. Slack permanently removes data from active production systems and ensures all backups are destroyed within 14 days.
5. Disaster Recovery
To provide continuous service and quickly restore its systems in the event of a failure or attack, Slack has implemented a comprehensive disaster recovery plan that covers the following:
- Production operations distributed across four physical locations to protect from loss of connectivity and location-specific failures.
- Replication of production transactions across the operating environments to ensure the app remains available in the event of a catastrophic event.
- Backup of production data in a remote location separate from the primary operating environment, enabling rapid restoration of operations if needed.
6. External Audits and Validation
Slack doesn’t expect users to blindly trust its high security claims. Independent third-party auditors regularly assess the app’s security to ensure maximum data protection and verify compliance with standards.
Over a dozen compliance certifications and attestations confirm the app’s commitment to strict and efficient security practices, including:
- ISO/IEC 27001, 27017, 27018, 27701, and 42001
- SOC 2 & 3
- CSA
Slack also employs independent entities for penetration testing at the app and infrastructure levels. These tests are conducted at least once a year and involve simulating attacks to find and exploit vulnerabilities. The goal is to develop solutions that make systems more resistant to unauthorized access.
Slack also welcomes its users to perform their own security assessments and testing. You can schedule these activities by reaching out to your account executive.
What Slack Security Concerns To Be Aware Of
The lack of E2EE is one of the most significant concerns for security-conscious users, but there are a few other issues to keep in mind, including:
- Third-party integration vulnerabilities: Slack integrates with thousands of apps to support collaboration and automation, but they represent potential security gaps. Malicious actors could use integrations as a point of entry to Slack, putting team communications at risk.
- Data sharing: In its privacy policy, Slack states that it may share some data with third parties, including advertisers. This could help malicious actors build a profile on you, which they can later leverage to conduct attacks.
- Exportable messages: Slack allows exporting messages from public channels on all plans. On Business+ and Enterprise plans, administrators can also export messages from private channels and direct messages. If malicious actors access your device, they could potentially steal these files and uncover highly confidential company information.
- Improper access management: Slack supports seamless collaboration, which often includes adding external collaborators such as freelancers or contractors. Risks can arise if access levels aren’t properly controlled. For example, adding a freelancer to a private channel where confidential management discussions occur can lead to leaks.
The Verdict: Is Slack Secure?
Despite the lack of E2EE, Slack implements advanced controls to ensure teams worldwide can use the app without worrying about data or user safety and privacy. In many cases, the level of security Slack provides largely depends on how you manage the app’s controls. There are several important actions you and your team can take to enhance security, such as:
Action | Explanation |
Using MFA | MFA provides an additional security layer, ensuring third parties can’t access your Slack even if they steal your password. |
Limiting guest user access | Limiting what guest users can see and do within your company’s Slack enhances data security, improves transparency, and simplifies management. |
Establishing clear access control policies | Clear access control policies ensure only authorized team members have access to confidential information, which minimizes internal threats. It also improves organization across channels and clarifies each member’s role. |
Vetting third-party integrations | Choosing verified and reputable third-party integrations minimizes the risk of security incidents and breaches. To address potential vulnerabilities, conduct regular integration audits and update your tech stack. |
Bonus read: Want to see if other popular apps provide reliable security? Check out our guides:
Why You Should Go Beyond App-Level Security
Slack may protect your files and conversations within the app, but they don’t shield you from network-level threats. Every message and file you send or receive goes through your network, such as Wi-Fi or mobile data. When this network relies on an outdated infrastructure, the risk of breaches and leaks increases.
If you frequently use Slack on your phone, that outdated infrastructure may belong to your mobile carrier. The biggest carriers in the U.S. have been the targets of data breaches and leaks in recent years, so you must take steps to strengthen your network-level protection and carefully choose the mobile carrier you’ll use alongside Slack or any other app.
A privacy-first mobile carrier such as Cape prioritizes security through minimal data collection, unique security and privacy features, and a proprietary mobile core.
Cape: The Carrier Built for Security and Privacy
Cape is a privacy-first mobile carrier designed to keep your communications safe from surveillance and misuse. Unlike traditional cell phone plan providers, our business model centers around providing you with premium and secure call, text, and data, rather than harvesting and selling your information.
Our service is built from the ground up with privacy and security at its core, offering unique features like:
Privacy & Security Feature | Description |
Cape doesn’t ask for your name, address, or Social Security number. We only collect the information necessary to provide service, and we retain that information for the minimum amount of time possible. | |
Traditional carriers rely on a fixed International Mobile Subscriber ID (IMSI) to connect your device to cellular networks. This is a vulnerability that lets carriers, advertisers, and bad actors identify and track your device. Cape lets subscribers automatically rotate their IMSI every 24 hours, making it infinitely more difficult to track you or your device. | |
Many services ask for your phone number, but sharing it exposes you to spam, scammers, data brokers, and a variety of other risks. VoIPs, on the other hand, don’t work with 2FA, cost extra, and aren’t encrypted. With Cape, you get two free additional SMS/MMS lines that are middle-to-end encrypted. | |
Most U.S. carriers store your call and text metadata for years, sometimes indefinitely. Cape is built to forget, so call data records (CDRs) are deleted after just 24 hours. | |
One-time passwords (OTP) can be intercepted by bad actors if SMS messages aren’t encrypted, exposing your bank accounts and other sensitive data. With Cape, you can encrypt and route all SMS/MMS messages through the Cape app, so even if they’re intercepted, nobody can read them. This feature is currently only available on iPhone. Android coming soon. | |
Cape nullifies the threat of SIM swapping by completely removing humans from the loop. During signup, you receive a 24-word phrase that generates a private key tied to your number. This effectively means that no one (but you) can move your number to a new carrier or device, not even Cape. | |
Legacy network protocols, like SS7, leave you vulnerable to hackers that can track your location, intercept your calls and texts, and steal sensitive information. Cape’s Network Lock relies on a proprietary signaling proxy to verify that your device’s physical location matches the network it’s trying to attach to. If we detect anything out of the ordinary, Cape automatically blocks the connection, nullifying the potential threat. | |
We don’t require your name or billing address. Payments are processed by Stripe and tokenized, so your subscription can’t be tied back to your personal details. | |
Traditional voicemail systems are outdated, unencrypted, and another security hole bad actors can exploit to gain access to your sensitive information. Cape encrypts all voicemails, ensuring only you can access them. | |
While roaming, your phone connects to local telecom providers to enable service. But, who knows who might be listening on the other end. Cape provides you with peace of mind by routing your traffic through our U.S.-based mobile core, ensuring your identity, data, and communications remain private and secure. |
Ditch Legacy Carriers: Get Cape Today
Cape is a “Heavy” Mobile Virtual Network Operator (MVNO), meaning we own our mobile core and provision our own SIMs. This gives us full control over how accounts are authenticated and what data is collected (and for how long), and is how we are able to provide privacy and security features no other carrier on the market can offer.
Get started with Cape today and enjoy the peace of mind, knowing you are fully protected against scammers, hackers, bad actors, and other mobile threats.
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