A Spammer is a standalone utility that allows to send massive
amounts unsolicited e-mails (SPAM) to different addresses. A
Spammer usually fakes e-mail message headers and uses anonymous
SMTP servers to send e-mails. These programs are not destructive.
In several countries usage of such tools is illegal.
Additional Details
There exist several anti-spammer tools that generate fake bounce
e-mail messages. That tricks some automated spammer tools to
exclude a 'bounced' e-mail address from their lists.
Most famous anti-spammer tools: Toxic Waste Dump.
Most famous spammer tools: ICQ-Spammer, AnonEBomber.
Disinfection
Allow F-Secure Anti-Virus to disinfect the relevant files.