Please
do not assume that newer versions of an application take security into
account.
Newer versions of LANguard require purchase.
Scanning
153
Lab 31: Target Scan through Firewall
Scan Open Ports of Target: Fscan
Prerequisites:
None
Countermeasures:
Host-based firewalls
Description:
The Fscan application is a tool from Foundstone that allows
an attacker to scan for open ports on targets. A unique feature of Fscan
is that it allows an attacker to scan in a random, ???quiet??? mode to try
to circumvent Intrusion Detection Software (IDS). Fscan also allows
the scan to be bound to a specific port??”for example, port 80, which
most firewalls allow. (This would be the ??“i option.)
Procedure:
From the Fscan application enter in the target IP address or
IP range and scan.
From a DOS prompt type the following with the syntax of:
fscan
(IP Address or Name) (Port #)
Unless otherwise instructed fscan will scan a default range of both Transfer
Control Protocol (TCP) and User Datagram Protocol (UDP) ports to see if the
ports are open. In this example the options of
??“qr
were used. This is the same
as saying
??“q ??“r
.
The
??“q
option instructs Fscan not to ping the target before scanning.
The
??“r
option instructs Fscan to scan in a random order.
These options help evade IDS that may be between the attacker and the target.
In this example, the target has several TCP ports open and a few UDP.
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