nmap -sS -P0 -sV -O <target>

2) Get list of servers with a specific port open

nmap -sT -p 80 -oG – 192.168.1.* | grep open

Change the -p argument for the port number. See “man nmap” for different ways to specify address ranges.

3) Find all active IP addresses in a network

nmap -sP 192.168.0.*

There are several other options. This one is plain and simple.

Another option is:

nmap -sP 192.168.0.0/24

for specific  subnets

4)  Ping a range of IP addresses

nmap -sP 192.168.1.100-254

nmap accepts a wide variety of addressing notation, multiple targets/ranges, etc.

5) Find unused IPs on a given subnet

nmap -T4 -sP 192.168.2.0/24 && egrep “00:00:00:00:00:00” /proc/net/arp

6) Scan for the Conficker virus on your LAN ect.

nmap -PN -T4 -p139,445 -n -v –script=smb-check-vulns –script-args safe=1 192.168.0.1-254

replace 192.168.0.1-256 with the IP’s you want to check.

7) Scan Network for Rogue APs.

nmap -A -p1-85,113,443,8080-8100 -T4 –min-hostgroup 50 –max-rtt-timeout 2000 –initial-rtt-timeout 300 –max-retries 3 –host-timeout 20m –max-scan-delay 1000 -oA wapscan 10.0.0.0/8

I’ve used this scan to successfully find many rogue APs on a very, very large network.

8) Use a decoy while scanning ports to avoid getting caught by the sys admin

sudo nmap -sS 192.168.0.10 -D 192.168.0.2

Scan for open ports on the target device/computer (192.168.0.10) while setting up a decoy address (192.168.0.2). This will show the decoy ip address instead of your ip in targets security logs. Decoy address needs to be alive. Check the targets security log at /var/log/secure to make sure it worked.

9) List of reverse DNS records for a subnet

nmap -R -sL 209.85.229.99/27 | awk ‘{if($3==”not”)print”(“$2″) no PTR”;else print$3″ is “$2}’ | grep ‘(‘

sudo nmap -F -O 192.168.0.1-255 | grep "Running: " > /tmp/os; echo "$(cat /tmp/os | grep Linux | wc -l) Linux device(s)"; echo "$(cat /tmp/os | grep Windows | wc -l) Window(s) devices"