CORRECT TEXT
Fill in the blank with the appropriate term.
______________ is an enumeration technique used to glean information about computer systems
on a network and the services running its open ports.

Answer: Banner grabbing

Explanation:

Banner grabbing is an enumeration technique used to glean information about computer systems
on a network and the services running its open ports. Administrators can use this to take inventory
of the systems and services on their network. An intruder however can use banner grabbing in
order to find network hosts that are running versions of applications and operating systems with
known exploits.
Some examples of service ports used for banner grabbing are those used by Hyper Text Transfer
Protocol (HTTP), File Transfer Protocol (FTP), and Simple Mail Transfer Protocol (SMTP); ports
80, 21, and 25 respectively. Tools commonly used to perform banner grabbing are Telnet, which is
included with most operating systems, and Netcat.
For example, one could establish a connection to a target host running a Web service with netcat,
then send a bad html request in order to get information about the service on the host:
[root@prober] nc www.targethost.com 80
HEAD / HTTP/1.1
HTTP/1.1 200 OK
Date: Mon, 11 May 2009 22:10:40 EST
Server: Apache/2.0.46 (Unix) (Red Hat/Linux)
Last-Modified: Thu, 16 Apr 2009 11:20:14 PST
ETag: “1986-69b-123a4bc6”

Accept-Ranges: bytes
Content-Length: 1110
Connection: close
Content-Type: text/html
The administrator can now catalog this system or an intruder now knows what version of Apache
to look for exploits.