I built an anti-spam email filtering stack a few decades ago [1] and we had great success using Rabin-Karp for exact-match filtering. It made it effectively fr

I built an anti-spam email filtering stack a few decades ago [1] and we had great success using Rabin-Karp for exact-match filtering. It made it effectively free to add more strings to check against, since we'd match against hundreds of thousands of strings in a single pass. It was only one tool in our arsenal but was really effective in allowing relatively untrained techs in our threat NOC to write rules for in-progress spam campaigns without needing to know regex or anything more complicated. We could usually get an RK rule into production within minutes of the first honeypot hit. [1] MX Logic, acquired by McAfee then shut down by Intel after their acquisition.