Exploit kits are toolkits used by attackers to manage exploits and deliver harmful programs to a vulnerable computer or device.
An exploit kit contains an inventory of exploits, each of which can take advantage of a flaw (vulnerability) in a program, computer or device. The kit itself is usually hosted on a harmful or a hacked site, so that any computer or device that visits the site is exposed to its effects.
When a new computer or device connects to the booby-trapped site, the exploit kit probes it for any flaws that can be affected by an exploit in the kit’s inventory. If one is found, the kit launches the exploit to take advantage of that vulnerability.
After the computer or device is compromised, the exploit kit can deliver a payload to it. This is usually another harmful program that is installed and launched on the computer or device, which in turn performs other unauthorized actions.
Exploit kits are designed to be modular and easy to use, so that their controllers can simply add or remove exploits and payloads to the toolkit.