Nessus is a male (of the second type-- his species has three sexes) character in Larry Niven's Known Space universe, of the species Pierson's Puppeteer, a herbivorous species noted for two heads whose mouths act as capable hands. Pierson's Puppeteers are technically advanced in most of the physical sciences.

Nessus is a remote security scanner for Linux, Solaris, FreeBSD, and Mac OS X. It is plugin-based and performs over 10,000 remote security checks. It allows for reports to be generated in HTML, and suggests a solution for each finding.