Barbarians at the Gate When discussing network security, many IT
professionals associate security technologies with network
access control mechanisms such as firewalls, proxy servers and
router access control lists. They’re designed to restrict the
flow of traffic into and out of corporate networks to reduce the
risk of compromise by malicious individuals on the Internet.
However, even the best filtering devices do very little to
protect a network if Internet-accessible devices are vulnerable
to attacks. Malicious individuals can use open communications
channels (such as HTTP, e-mail and DNS) to compromise a system
on a network remotely, and use that compromised system as a
launching pad to attack and compromise other “trusted” systems
on the network. Many of today’s IT infrastructures have become
so large, complex and geographically dispersed that IT managers
may not learn about the defacement of their Web page in a
foreign data center for several days. In the case of one
organization, an IT manager learned