Service uptime and availability is a crucial factor that determines the success of online businesses. In a rapidly evolving world, it is important that transactions remain productive, and they help clients meet their business goals in a timely manner. A downtime in service availability is a form of attack known as Denial of Service. In this article, we will be learning about a specific form of Denial-of-Service attack that can be caused by regular expression malfunctioning. In a Snyk report published in 2019, ReDoS attack has spiked by 143% in Node applications. To better understand ReDoS, or Regex DOS, let us understand some under-the-hood concepts about Regular Expressions and how are they consumed in modern web applications.   Regular Expressions: A Primer A regular expression is a pattern consisting of a sequence of characters that define a search pattern. They are a powerful tool for manipulating text, but they can....