Lists of vulnerabilities and exploit kits make it significantly easier to develop custom malware. Cyber attacks can be automated to allow the use of drive-by downloads or other methods of distribution by simple means that require no expert knowledge. Attackers may exploit known vulnerabilities of a web browser or related resources or extensions to prepare subsequent attacks, or to load and install malicious code on a client. Malicious code loaded onto clients in this way often causes further malware to be loaded, which is then executed on the clients with user privileges.