Credential detector
Slack bot token: format and detection
Short answer
A Slack bot token starts with xoxb-, followed by two numeric parts of 10 to 13 digits separated by a hyphen, then more letters, digits and hyphens. Maskflare matches that shape with an entropy floor of 3.0.
What it is
A bot token lets an application act as a Slack bot in a workspace. The Credentials pack masks it by default, with sibling detectors for user tokens, app tokens, legacy tokens and webhook URLs.
In Maskflare this is the detector slack_bot_token, labelled "Slack bot token", category password or access key, in the Credentials pack.
Format
- The literal prefix xoxb-.
- 10 to 13 digits, a hyphen, 10 to 13 digits.
- Any further letters, digits and hyphens (the trailing secret part).
How Maskflare recognises it
Prefix, the two numeric parts and an entropy floor of 3.0 on the whole token. The pattern has no fixed total length because the trailing part varies.
Why this page shows no sample key
A realistic sample key would look like a live credential to secret scanners and to anyone skimming the page, and an obviously fake one would not pass this detector's length and entropy rules. The format above is enough to recognise the key: the prefix, the length and the character set.
Regex and validation caveats
- Because the tail is open-ended, the match runs to the first character outside letters, digits and hyphen.
- A token cut short after the second numeric part still matches.
How to detect it in LLM traffic
Tokens leak through bot configuration files, deployment manifests and chat-ops scripts.
Maskflare reads the whole request body, including the system prompt, earlier messages and tool arguments, and replaces each match with a token such as mf_mask_d7e0 before the request goes out. Coding agents are covered through hooks that mask tool inputs and results, so a key printed by a shell command does not travel onward in the next prompt. On ChatGPT, browser protection blocks prompts that contain API keys, tokens or private keys outright.
If you build the detection yourself
- Scan the raw text rather than parsed fields: keys sit in code, JSON strings, headers, shell output and pasted logs, often with no label at all.
- Match the prefix and the exact length for the Slack bot token. Where the key has no fixed prefix, require the provider's name and an assignment next to the value instead of matching any long string.
- Compute the Shannon entropy of the candidate and reject low values, and keep an allow list of placeholders (${KEY}, repeated characters, the alphabet run), because documentation and templates are full of them.
- Mask the value before the text is sent anywhere. If the key was already sent, treat it as exposed and rotate it; masking later does not recall it.
How Maskflare handles it
- Protect now, Finance - Protect now, Healthcare, Developer and Monitor first: mask (a reversible token).
The available actions are mask (reversible token), redact, partial, hash, format-preserving encryption, generalize, alert and block. Masked values are kept encrypted for 30 days so that answers can be restored, then they expire; prompts and responses are not logged. The full list of detectors is in the detector reference.
Compliance profiles that include it
All 6 compliance profiles include the Credentials pack, and applying them turns this detector on: HIPAA Safe Harbor, GDPR - EU/EEA, UK GDPR, PCI DSS, US personal data and Switzerland - nDSG health data. A profile is a floor: it never turns anything off or weakens a rule that is already stricter.
Frequently asked questions
Does Maskflare detect Slack webhook URLs?
Yes, through a separate slack_webhook_url detector.
Why is there no total length for a Slack token?
The catalogue's pattern allows a variable-length tail after the numeric parts.
Is the Slack bot token detector on by default?
Yes. It belongs to the Credentials pack, which the default Protect now template turns on with the action mask.
Does Maskflare store the keys it masks?
Prompts and responses are not logged. A masked value is kept encrypted for 30 days so the answer can be restored, then it expires.
Rules on this page describe what Maskflare's detectors and validators check. They are read from the detection catalogue and are not the specification of the body that issues the identifier. No sample key is shown on purpose.