Regular Expression Denial of Service has existed for well over a decade, but has not received the love it deserves lately. There are some proof of concept attacks out there currently, most of which are ineffective due to implementation optimizations. Regardless of the effectiveness most of these PoC's are geared only to NFA engines. This talk will demonstrate working PoC's that bypass optimizations. Both NFA and DFA engines will get love. Tools will be released (with demonstration) that benchmark NFA/DFA engines and automate creation of 'evil strings' given an arbitrary regular expression. Attendees can expect a review of regex and a deep under the hood explanation of both regex engines before abuses ensue. ^ Not a security researcher