Even as security has grown ever stronger and the techniques to catch criminals are more advanced than ever, serial killers still find a way to conduct their murderous business. In the 21st century, violent killers have used modern technology to help them commit their horrific crimes. Some look to the internet to stalk their victims, while the dark web is home to a shadowy world of illegal weapon sales, murder-for-hire sites and criminal forums providing tips on how to kill and get away with it.

This book includes:

• Philip Markoff, aka the Craigslist Killer, who used the e-commerce site Craigslist to solicit victims

• Stephen Paddock, who killed 60 people and injured nearly 1,000 more after opening fire at a music festival in Las Vegas

• Maury Travis, who sent a map with his victims' locations to the detectives on the case, daring them to find the man behind the murder.