Distributed Denial of Service (DDoS) and Denial of Service (DoS) attacks share one primary attribute – a method is used to disrupt the normal operations of a web service (or application) via the saturation, corruption, or exploitation of other services used to support the normal operation of the application. After that, the word “Distributed” adds multiple layers of complexity to the attack that take it to an entirely different level. In this blog, I will explain DoS and DDoS, identify best practices for mitigating those risks, and make it real with a personal story where DoS impacted me.
DoS and DDoS Explained
Typically, a Denial of Service is very focused on one service, vendor, or web application and may be executed from a few assets easily identifiable by geolocation, IP address, or protocol. DoS attacks can easily be mitigated with security solutions, IP filtering, ISP MAC address filtering, next generation firewalls, and even cloud content filtering services.
Distributed Denial of Service has fundamentally the same attributes as multiple layers of obfuscation to the attack. It is typically conducted using multiple devices, network traffic is not easily discernable between good requests and bad requests, and identifying source IP addresses does not provide a reliable method for mitigating the attack due techniques to spoof the source address or randomize the contents of the attack vector. The attack against DYN on October 21, 2016 is a typical example of DDoS against DNS services that had ramifications across the Internet via compromised IoT devices. Unfortunately, this is the type of attack that worries most businesses verses a typical DoS targeted attack that has long standing mitigation best practices.
Best Practices for Mitigating the Risks of DoS and DDoS Attacks
Any company worried about the attacks from last week should consider the following as a matter of best practice to aid in the mitigation of DoS and DDoS attacks:
- Register your website with more than one provider. A single DDoS attack against one hopefully will not impact another.
- Stress test your web application. Before going live on your web application or web service, perform a web application vulnerability assessment and stress test to identify thresholds that could cause a DoS against your environment. Understanding how much you can actually handle is key to limiting connections or sessions so a DoS does not take down your environment. If you have never done this, plan to do it.
- Ensure all web applications and services, including IoT devices, are behind a firewall. Assets should never be connected directly to the internet unless they are actually designed to be (like a firewall). This limits communications directly to them that can be used in a DoS attack.
- Identify if your ISP, web service hosting provider, or other security vendors can filter traffic and limit exposure to DoS and DDoS attacks. Sometimes a simple security tool blocking bad traffic can mean all the difference in the world.
A Real Example of How DoS can Impact You
Without performing some of these basic security steps, any type of real world problem can happen. In fact, it happened to me. On Black Friday a few years ago I received a ridiculously great men’s clothing offer from a site I frequent. I made a sizable purchase for my myself and some of my children, and received an order confirmation and nothing more. A few days later, I did not receive a shipping notification so I called the company and they indicated that they had such a response to the offer, it crashed their servers (A good DoS, right?). I provided my order number, and just to make sure I gave them the exact contents of the original order; they said they would honor the price. A few hours later, I received a second confirmation number. Well, to my surprise I began receiving duplicate, and even triplicate, items due to both confirmation numbers being active although my credit card was only charged once. I called the company again and they said to keep the extra merchandise. The recovery of the DoS attack caused duplicate and even triplicate orders and it was too much for their IT department to sort out. They could not track who was sent what. It was a happy holiday indeed.
DDoS and DoS can have a wide range of implications for any business or service. While I was personally lucky in the story above, I cannot even gauge how much in losses the clothing company faced due a legitimate DoS from people willing to spend their money. The attack on October 21, 2016 is still being tallied for losses but every company, big or small, can take a few basic steps to ensure they are not an unsuspecting victim.