A computer program carrying out some task on behalf of a user, such as delivering a Web page or sending email messages. Computers on which these server applications are found are also called servers.
Servers have often been the focus of computer security attacks. For example, on March 8, 2005, a security researcher announced in an advisory that Microsoft Corporation’s newest operating systems are vulnerable to Denial of Service (DoS) attacks. In particular, researcher Dejan Lavaja said that Windows Server 2003 and XP Service Pack 2 (with the Windows Firewall not on) could suffer from LAND attacks—remote DoS incidents created when a packet is sent to a computer on which the source host/port is the same as the destination host/port. Using reverse-engineering tools, this researcher discovered that just one LAND packet transmitted to a file server could result in “frozen” Windows Explorers on all the workstations connected to that server. In fact, warned Lavaja, because of this vulnerability the network could totally collapse.
Soon thereafter, however, a spokesperson for the Microsoft Corporation said that although the vulnerability exists, the adverse impact of such an attack would result only in the computer’s running sluggishly for a brief period. Users were cautioned to filter traffic with the same IP source and destination address.
Naraine, R. Old-School DoS Attack Can Penetrate XP SP2. [Online, March 8, 2005.] Ziff Davis Publishing Holdings Inc. Website. http://www.eweek.com/article2/ 0,1759,1773958,00.asp.