Neutralizing Zombies and Controlling Outbound Spam Solution Brief
Email blacklisting and loss of email services are a direct result of outbound spam. Outbound spam also leads to complaints about network abuse and increased demand for helpdesk support and engineering resources. Since most spam originates from zombie PCs (80–90% according to industry experts), large email service providers with difficult-to-control users, such as ISPs and tertiary institutions, tend to suffer most from outbound spam. Other types of background zombie activity such as IP scanning creates additional load on the network, which is particularly undesirable when these links are operated at high utilization.