Overview
Let's Encrypt is a monitoring bot used for security scanning, malware checks, vulnerability assessment, certificate review, and site-safety analysis.
Its primary user-agent pattern is https://www.letsencrypt.org; a representative HTTP user-agent is Mozilla/5.0 (compatible; Let's Encrypt validation server; +https://www.letsencrypt.org).
Let's Encrypt is verified with Medium confidence. The identity type is Verified Bot, and the evidence basis is a public crawler reference or source-linked documentation.
Let's Encrypt is marked as not reliably governed by robots.txt directives; use server-side rules if the traffic should be restricted.
Let's Encrypt can usually be allowed after confirming the source and monitoring request volume.
Identity
- User-Agent
https://www.letsencrypt.org- HTTP Agent Examples
Mozilla/5.0 (compatible; Let's Encrypt validation server; +https://www.letsencrypt.org)- Robots.txt Token
https://www.letsencrypt.org- Identity Type
- Verified Bot
- Evidence Method
- Verify Let's Encrypt by matching `https://www.letsencrypt.org` to a public crawler reference or source-linked documentation, then checking reverse DNS, IP ownership, request behavior, and crawl consistency.
Classification
- Type
- Security
- Kind
- Monitor
- Family
- Let's Encrypt
- Purpose
- security
Behavior and handling
- Common Use
- Let's Encrypt is used for security scanning, malware checks, vulnerability assessment, certificate review, and site-safety analysis.
- Detection Notes
- Let's Encrypt traffic is primarily detected by the `https://www.letsencrypt.org` user-agent pattern; a representative HTTP user-agent is `Mozilla/5.0 (compatible; Let's Encrypt validation server; +https://www.letsencrypt.org)`. Compare source IPs, reverse DNS, request paths, and crawl cadence before trusting the traffic.
- Respects robots.txt
- No
- Spoofing Risk
- Let's Encrypt has medium spoofing risk because user-agent strings can be copied; pair the match with DNS, IP, behavior, or operator evidence.
- Risk
- Safe
- Recommended Handling
- No
Rules and controls
- Robots.txt Snippet
# This agent may ignore robots.txt. Use authenticated access controls or network policy when blocking is required.