Description:
The Telnet application normally uses port 23 but can be
used to obtain specific banner information from other running services
by connecting to other ports on the target. An attacker uses this information
to launch appropriate attacks for the results obtained. Remember
that all Linux commands are
case sensitive
.
Procedure:
From a DOS prompt or Linux shell, type the following with
the syntax of:
telnet (IP Address or Name)(Port #)
In this example, the Telnet application is attempting to connect to port 80,
the standard HTTP (Web) port. The results show that IIS 5.0 is being used by
the target.
66
Practical Hacking Techniques and Countermeasures
???Banner grabbing??? via Telnet works in Linux as well. In this example Telnet
is connecting to port 21.
The results show that Serv-U FTP Server, version 5.0 is being used at the target.
Banner Identification
67
Lab 2: Banner Identification
Banner Grabbing:
NETCAT
Prerequisites:
None
Countermeasures:
Uninstall/disable unnecessary services, SSH, VPN,
IPSEC, banner alteration.
Description:
The netcat application has many uses and can be used to
obtain specific banner information from services by connecting to
specific ports on the target. An attacker uses this information to launch
appropriate attacks for the results obtained. The netcat application is
used throughout this book. Remember that all commands in Linux are
case sensitive
.
Procedure:
From a DOS prompt or Linux terminal, type the following
with the syntax of:
nc
(IP Address)(Port #)
To use netcat on Microsoft Windows:
From the directory containing the netcat application type the following:
nc ??“v ??“n (Target IP Address) (Port #)
In this example the netcat application is attempting to grab the banner
information from the target on port 80, the standard HTTP (Web) port.
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