• 106 | Chapter 3: Reconnaissance
  • Learning Kali Linux




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    High-Speed Scanning
    nmap
    may be the de facto port scanner, but it is not the only scanner that’s available.
    In some cases, you may find you have large networks to scan. 
    nmap
    is efficient, but it
    isn’t optimized for scanning very large networks. One scanner that is designed for
    scanning large networks is 
    masscan
    . A major difference between 
    masscan
    and 
    nmap
    is that 
    masscan
    uses asynchronous communication: the program will send a message,
    and rather than waiting for the response to come back, it will keep sending. It uses
    another part of the program to wait for the responses and record them. Its ability to
    transmit at high rates of speed allows it to scan the entire internet in a matter of
    minutes. Compare this with the speed of scanning just a local /24 network with a
    maximum of 254 hosts using 
    nmap
    .
    106 | Chapter 3: Reconnaissance


    masscan
    can take different parameters, but it accepts the ones that 
    nmap
    also accepts.
    If you know how to operate 
    nmap
    , you can pick up 
    masscan
    quickly. One difference
    between 
    masscan
    and 
    nmap
    , which you can see in 
    Example 3-19
    , is the need to spec‐
    ify ports. 
    nmap
    will assume a set of ports to use. 
    masscan
    doesn’t assume any ports. If
    you try to run it without telling it which ports to scan, it will prompt you to specify
    the ports you want to scan. In 
    Example 3-19
    , you will see I set to scan the first 1,501
    ports. If you were looking for all systems listening on port 443, meaning that system
    was likely operating a TLS-based web server, you would specify that you wanted to
    scan only port 443. Not scanning ports you don’t care about will save you a lot of
    time.
    Example 3-19. High-speed scanning with masscan
    root@rosebud:~# masscan -sS --ports 0-1500 192.168.86.0/24
    Starting masscan 1.0.3 
    (
    http://bit.ly/14GZzcT
    )
    at 2017-12-31 20:27:57 GMT
    -- forced options: -sS -Pn -n --randomize-hosts -v --send-eth
    Initiating SYN Stealth Scan
    Scanning 
    256
    hosts 
    [
    1501
    ports/host
    ]
    Discovered open port 445/tcp on 192.168.86.170
    Discovered open port 22/tcp on 192.168.86.30
    Discovered open port 1410/tcp on 192.168.86.37
    Discovered open port 512/tcp on 192.168.86.239
    Discovered open port 445/tcp on 192.168.86.239
    Discovered open port 22/tcp on 192.168.86.46
    Discovered open port 143/tcp on 192.168.86.238
    Discovered open port 1410/tcp on 192.168.86.36
    Discovered open port 53/tcp on 192.168.86.1
    Discovered open port 1400/tcp on 192.168.86.36
    Discovered open port 80/tcp on 192.168.86.38
    Discovered open port 80/tcp on 192.168.86.1
    You can use a multipurpose utility for port scanning that will also give you some con‐
    trol over the time interval between messages being sent. Whereas 
    masscan
    uses an
    asynchronous approach to speed things up, 
    hping3
    gives you the ability to specify the
    gap between packets. This doesn’t give it the capacity to do really high-speed scan‐
    ning, but 
    hping3
    does have a lot of power to perform many other tasks. 
    hping3
    allows
    you to craft a packet with command-line switches. The challenge with using 
    hping3
    as
    a scanner is that it is really a hyperactive ping program and not a utility trying to re-
    create what 
    nmap
    and other scanners do.
    However, if you want to perform scanning and probing against single hosts to deter‐
    mine characteristics, 
    hping3
    is an outstanding tool. 
    Example 3-20
     is a SYN scan
    against 10 ports. The 
    -S
    parameter tells 
    hping3
    to set the SYN flag. We use the 
    -p
    flag
    to indicate the port we are going to scan. By adding the 
    ++
    to the 
    -p
    flag, we’re telling
    hping3
    that we want it to increment the port number. We can control the number of

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