Provided by: nmap_6.40-0.2ubuntu1_amd64 bug


       ndiff - Utility to compare the results of Nmap scans


       ndiff [options] {a.xml} {b.xml}


       Ndiff is a tool to aid in the comparison of Nmap scans. It takes two Nmap XML output files
       and prints the differences between them. The differences observed are:

       ·   Host states (e.g. up to down)

       ·   Port states (e.g. open to closed)

       ·   Service versions (from -sV)

       ·   OS matches (from -O)

       ·   Script output

       Ndiff, like the standard diff utility, compares two scans at a time.


       -h, --help
           Show a help message and exit.

       -v, --verbose
           Include all hosts and ports in the output, not only those that have changed.

           Write output in human-readable text format.

           Write output in machine-readable XML format. The document structure is defined in the
           file ndiff.dtd included in the distribution.

       Any other arguments are taken to be the names of Nmap XML output files. There must be
       exactly two.


       Let's use Ndiff to compare the output of two Nmap scans that use different options. In the
       first, we'll do a fast scan (-F), which scans fewer ports for speed. In the second, we'll
       scan the larger default set of ports, and run an NSE script.

           # nmap -F -oX scanme-1.xml
           # nmap --script=html-title -oX scanme-2.xml
           $ ndiff -v scanme-1.xml scanme-2.xml
           -Nmap 5.35DC1 at 2010-07-16 12:09
           +Nmap 5.35DC1 at 2010-07-16 12:13

            Host is up.
           -Not shown: 95 filtered ports
           +Not shown: 993 filtered ports
            22/tcp    open   ssh
            25/tcp    closed smtp
            53/tcp    open   domain
           +70/tcp    closed gopher
            80/tcp    open   http
           +|_ html-title: Go ahead and ScanMe!
            113/tcp   closed auth
           +31337/tcp closed Elite

       Changes are marked by a - or + at the beginning of a line. We can see from the output that
       the scan without the -F fast scan option found two additional ports: 70 and 31337. The
       html-title script produced some additional output for port 80. From the port counts, we
       may infer that the fast scan scanned 100 ports (95 filtered, 3 open, and 2 closed), while
       the normal scan scanned 1000 (993 filtered, 3 open, and 4 closed).

       The -v (or --verbose) option to Ndiff made it show even the ports that didn't change, like
       22 and 25. Without -v, they would not have been shown.


       There are two output modes: text and XML. Text output is the default, and can also be
       selected with the --text option. Text output resembles a unified diff of Nmap's normal
       terminal output. Each line is preceded by a character indicating whether and how it
       changed.  - means that the line was in the first scan but not in the second; + means it
       was in the second but not the first. A line that changed is represented by a - line
       followed by a + line. Lines that did not change are preceded by a blank space.

       Example 1 is an example of text output. Here, port 80 on the host gained a service version (lighttpd 1.5.0). The host at changed its reverse DNS name. The host at was completely absent
       in the first scan but came up in the second.

       Example 1. Ndiff text output

           -Nmap 4.85BETA3 at 2009-03-15 11:00
           +Nmap 4.85BETA4 at 2009-03-18 11:00

            Host is up.
            Not shown: 99 filtered ports
           -80/tcp open  http
           +80/tcp open  http    lighttpd 1.5.0

            Host is up.
            Not shown: 100 filtered ports

           +Host is up.
           +Not shown: 98 filtered ports
           +80/tcp  open  http     Apache httpd 1.3.41.fb1
           +443/tcp open  ssl/http Apache httpd 1.3.41.fb1

       XML output, intended to be processed by other programs, is selected with the --xml option.
       It is based on Nmap's XML output, with a few additional elements to indicate differences.
       The XML document is enclosed in nmapdiff and scandiff elements. Host differences are
       enclosed in hostdiff tags and port differences are enclosed in portdiff tags. Inside a
       hostdiff or portdiff, a and b tags show the state of the host or port in the first scan
       (a) or the second scan (b).

       Example 2 shows the XML diff of the same scans shown above in Example 1. Notice how port
       80 of is enclosed in portdiff tags. For, the
       old hostname is in a tags and the new is in b. For the new host, there is a
       b in the hostdiff without a corresponding a, indicating that there was no information for
       the host in the first scan.

       Example 2. Ndiff XML output

           <?xml version="1.0" encoding="UTF-8"?>
           <nmapdiff version="1">
                   <status state="up"/>
                   <address addr="" addrtype="ipv4"/>
                     <hostname name=""/>
                     <extraports count="99" state="filtered"/>
                       <port portid="80" protocol="tcp">
                         <state state="open"/>
                           <service name="http"/>
                           <service name="http" product="lighttpd" version="1.5.0"/>
                   <status state="up"/>
                   <address addr="" addrtype="ipv4"/>
                       <hostname name=""/>
                       <hostname name=""/>
                     <extraports count="100" state="filtered"/>
                     <status state="up"/>
                     <address addr="" addrtype="ipv4"/>
                       <extraports count="98" state="filtered"/>
                       <port portid="80" protocol="tcp">
                         <state state="open"/>
                         <service name="http" product="Apache httpd"
                       <port portid="443" protocol="tcp">
                         <state state="open"/>
                         <service name="http" product="Apache httpd" tunnel="ssl"


       Using Nmap, Ndiff, cron, and a shell script, it's possible to scan a network daily and get
       email reports of the state of the network and changes since the previous scan.  Example 3
       shows the script that ties it together.

       Example 3. Scanning a network periodically with Ndiff and cron

           OPTIONS="-v -T4 -F -sV"
           date=`date +%F`
           cd /root/scans
           nmap $OPTIONS $TARGETS -oA scan-$date > /dev/null
           if [ -e scan-prev.xml ]; then
                   ndiff scan-prev.xml scan-$date.xml > diff-$date
                   echo "*** NDIFF RESULTS ***"
                   cat diff-$date
           echo "*** NMAP RESULTS ***"
           cat scan-$date.nmap
           ln -sf scan-$date.xml scan-prev.xml

       If the script is saved as /root/, add the following line to root's crontab:

           0 12 * * * /root/


       The exit code indicates whether the scans are equal.

       ·   0 means that the scans are the same in all the aspects Ndiff knows about.

       ·   1 means that the scans differ.

       ·   2 indicates a runtime error, such as the failure to open a file.


       Report bugs to the nmap-dev mailing list at <>.


       Ndiff started as a project by Michael Pattrick during the 2008 Google Summer of Code.
       Michael designed the program and led the discussion of its output formats. He wrote
       versions of the program in Perl and C++, but the summer ended shortly after it was decided
       to rewrite the program in Python for the sake of Windows (and Zenmap) compatibility. This
       Python version was written by David Fifield. James Levine released[1] a Perl script named
       Ndiff with similar functionality in 2000.


       David Fifield <>

       Michael Pattrick <>



        1. released