A network investigative technique, also known as NIT, is a tool used by law enforcement to track down and catch bad guys who use the internet to do bad things.
Let's say you have a neighbor who you suspect is stealing cookies from your kitchen when you're not home. You can't catch them in the act, but you can set a trap for them. You leave a trail of cookies out to lure them in, and then when they take the bait, you have evidence that they stole the cookies.
That's kind of like what NIT does, except it's for catching people who are doing much more serious things online, like selling illegal drugs or sharing child pornography.
The way it works is the FBI or other law enforcement agency finds a website or online forum where they suspect people are doing bad things. They then set up a trap on the website, like a fake advertisement or an infected image file, that when clicked on, secretly installs a program on the user's computer. This program allows the FBI to track everything the user does on their computer, like what websites they visit or what files they download.
Using this information, the FBI can then gather evidence against the user and make an arrest.
Now, it's important to note that some people think using NIT is kind of like cheating, since it involves tricking people into giving up information. However, the FBI says they only use NIT when they have a warrant to do so, and that it's an important tool for catching serious criminals who might otherwise be able to hide behind the anonymity of the internet. And just like setting a trap for your cookie-stealing neighbor, it's all about catching someone who is doing something wrong.