Malvertising is an attack vector that delivers malware through online advertisements. Attackers either purchase ad placements on legitimate websites or compromise existing ad networks. The manipulated ads can redirect users to exploit kits or trigger drive-by downloads. Even trustworthy websites can serve malicious ads because the advertisements are delivered through third-party networks. Defenses include ad blockers on corporate devices, keeping browsers up to date, and strict patch management for browser plug-ins.