CAPTCHA stands for Completely Automated Public Turing test to tell Computers and Humans Apart. The most commonly viewed CAPTCHAs are sequential letters and numbers displayed as graphics that you have to correctly feed into a text input.
If you let anyone sign up for an account on your Jenkins server, then the last thing you want are bots (automated scripts) creating accounts. Bots have an economy of scale, being able to scan the internet rapidly and never getting bored. CAPTCHAs are a necessary defense against these dumb attacks.
The negative purposes of bots are as follows:
- Performing a Denial Of Service (DOS) attack on your server, for example, by automatically creating numerous heavyweight jobs
- Distributed Denial Of Service attack (DDOS) on other servers by harvesting many Jenkins servers to fire off large numbers of requests
- Injecting unwanted...