Exploit kits are automated cybercrime tools that scan systems for weaknesses and deploy malware like ransomware or spyware. Delivered through compromised websites, malicious ads, or infected attachments, these kits identify vulnerabilities in outdated software, browsers, or plugins. Notorious examples like Angler and Rig have historically exploited weaknesses in programs such as Adobe Flash and Internet Explorer. Defenses against these threats include keeping software updated, using secure browsers with fewer plugins, and implementing strong endpoint and network security measures, alongside user education about online threats.