Wireless Network are the most easy as well as desirable target for wannabe hackers. Ever wondered that someone might be leeching of your hard paid wifi network? You may opt out for an expensive way to keep the hackers away by buying hacker-proof wallpapers for your home but that really is far fetched. An easy and free way is to scan your network for the device connected with it. This way you can find out if some unknown or unwanted device is connected to it.
We will use terminal for finding out what devices are connected to your network in Linux. The process is very simple and easy to use even for beginners. Here we go:
Get nmap:
nmap is one of the most popular network scanning tool in Linux. Use the following command to install nmap in Ubuntu:
sudo apt-get install nmap
Get IP range of the network:
Now we need to know the IP address range of the network. Use the ifconfig command to find it out. Look for wlan0 if you are using wifi or eth0 if you are using Ethernet.
user@user-notebook:~$ ifconfig
wlan0 Link encap:Ethernet HWaddr 70:f1:a1:c2:f2:e9
inet addr:192.168.1.91 Bcast:192.168.1.255 Mask:255.255.255.0
inet6 addr: fe80::73f1:a1ef:fec2:f2e8/64 Scope:Link
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
RX packets:2135051 errors:0 dropped:0 overruns:0 frame:0
TX packets:2013773 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:1000
RX bytes:1434994913 (1.4 GB) TX bytes:636207445 (636.2 MB)
The important things are highlighted in bold. As you see my IP is 192.168.1.91 and the subnet mask is 255.255.255.0 which means that the ip address range on my network varies from 192.168.1.0 to 192.168.1.255.
Scan the network:
It is advisable to use root privileges while scanning the network for more accurate information. Use the nmap command in following way:
user@user-notebook:~$ sudo nmap -sP 192.168.1.0/24
Starting Nmap 5.21 ( http://nmap.org ) at 2012-09-01 21:59 CESTNmap scan report for neufbox (192.168.1.1)
Host is up (0.012s latency).
MAC Address: E0:A1:D5:72:5A:5C (Unknown)
Nmap scan report for takshak-bambi (192.168.1.91)
Host is up.
Nmap scan report for android-95b23f67te05e1c8 (192.168.1.93)
Host is up (0.36s latency).
As you can see there three devices connected to my network. The router itself, my laptop and my Galaxy S2. What is connected to your network?
from：http://itsfoss.com/how-to-find-what-devices-are-connected-to-network-in-ubuntu/