Corporate mail services are designed to perform better than public mail
services. Fast mail delivery, large size file transfer as an attachments, high
level spam and virus protection, commercial advertisement free environment are
some of the advantages worth to mention. But these mail services are frequent
target of hackers and spammers. Distributed Denial of service attacks are
becoming more common and sophisticated. The researchers have proposed various
solutions to the DDOS attacks. Can we stop these kinds of attacks with
available technology? These days the DDoS attack through spam has increased and
disturbed the mail services of various organizations. Spam penetrates through
all the filters to establish DDoS attacks, which causes serious problems to
users and the data. In this paper we propose a novel approach to defend DDoS
attack caused by spam mails. This approach is a combination of fine tuning of
source filters, content filters, strictly implementing mail policies,educating
user, network monitoring and logical solutions to the ongoing attack. We have
conducted several experiments in corporate mail services; the results show that
this approach is highly effective to prevent DDoS attack caused by spam. The
novel defense mechanism reduced 60% of the incoming spam traffic and repelled
many DDoS attacks caused by spam.