In a
full-connect scan
,
nmap
completes the three-way
handshake before closing the
connection. One advantage to this type of scan is that applications aren’t getting half-
open connections across the server. There is a slim chance that this may be less suspi‐
cious to a monitoring system or team than the half-open connections. There would
be no differences in the results between a full-connect and a half-open scan. It comes
down to which is more polite and potentially less likely to be noticed. In
Example 3-16
, you can see partial results from a full-connect scan. In this example,
I’m using
nmap
to scan the entire network. The
/24
designation tells
nmap
to
scan all
hosts from 192.168.86.0-255. This is one way of denoting that. You can also provide
ranges or lists of addresses if that’s what you need to do.
Example 3-16. Full connect nmap scan
root@rosebud:~# nmap -sT -T
5
192.168.86.0/24
Nmap
scan report
for
testwifi.here
(
192.168.86.1
)
Host is up
(
0.00092s latency
)
.
Not shown:
995
closed ports
PORT
STATE SERVICE
53/tcp open domain
80/tcp open http
5000/tcp open upnp
8080/tcp open http-proxy
8081/tcp open blackice-icecap
MAC Address: 18:D6:C7:7D:F4:8A
(
Tp-link Technologies
)
Nmap scan report
for
myq-d9f.lan
(
192.168.86.20
)
Host is up
(
0.0064s latency
)
.
Not shown:
999
closed ports
PORT STATE SERVICE
80/tcp open http
MAC Address: 64:52:99:54:7F:C5
(
The Chamberlain Group
)
In the output,
nmap
provides not only the port number but also the service. This ser‐
vice name comes from a list
of service identifiers that
nmap
knows and has nothing
to do with what may be running on that port.
nmap
can determine which service is
running on the port by getting application responses.
nmap
also helpfully provides a
lookup of the vendor ID from the MAC address. This vendor ID can help you iden‐
tify the device you are looking at. The first one, for instance, is from Tp-Link Tech‐
nologies. Tp-Link makes network hardware like wireless access point/router devices.
You may have noticed that I didn’t specify ports I wanted to scan. By default,
nmap
will scan the 1,000 most commonly used ports. This makes the scan faster than scan‐
ning all 65,536 ports, since you won’t see the vast majority of those ports in use. If you
want
to specify ports, you can use ranges or lists. If you want to scan all the ports, you
can use the command-line switch
-p-
. This tells
nmap
to scan everything;
nmap
also
has a default speed at which it scans. This is the delay between messages that are sent.
