RubyGems is the package registry and distribution system for Ruby libraries, called gems. Developers use it to find, download, and install code dependencies into applications and build environments. Because it is part of the standard Ruby workflow, RubyGems is a trusted path into developer systems and CI pipelines.
That trust makes RubyGems important in cyber security. A malicious gem can look like an ordinary dependency while actually running code during installation or build time, which turns package management into an execution path. Attackers use this to deliver payloads, steal secrets, or compromise developer machines. Defenders reduce risk by pinning versions, reviewing new dependencies, using approved mirrors or allowlists, and treating unexpected gem installs as security-relevant events.