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NAME | SYNOPSIS | DESCRIPTION | OPTIONS SUMMARY | EXAMPLE | OUTPUT | PERIODIC DIFFS | EXIT CODE | BUGS | HISTORY | AUTHORS | WEB SITE | NOTES | COLOPHON |
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NDIFF(1) User Commands NDIFF(1)
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.
--text
Write output in human-readable text format.
--xml
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 scanme.nmap.org -oX scanme-1.xml
# nmap --script=html-title scanme.nmap.org -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
scanme.nmap.org (64.13.134.52):
Host is up.
-Not shown: 95 filtered ports
+Not shown: 993 filtered ports
PORT STATE SERVICE VERSION
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
photos-cache-snc1.facebook.com gained a service version (lighttpd
1.5.0). The host at 69.63.179.25 changed its reverse DNS name.
The host at 69.63.184.145 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
photos-cache-snc1.facebook.com (69.63.178.41):
Host is up.
Not shown: 99 filtered ports
PORT STATE SERVICE VERSION
-80/tcp open http
+80/tcp open http lighttpd 1.5.0
-cm.out.snc1.tfbnw.net (69.63.179.25):
+mailout-snc1.facebook.com (69.63.179.25):
Host is up.
Not shown: 100 filtered ports
+69.63.184.145:
+Host is up.
+Not shown: 98 filtered ports
+PORT STATE SERVICE VERSION
+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 photos-cache-snc1.facebook.com
is enclosed in portdiff tags. For 69.63.179.25, the old hostname
is in a tags and the new is in b. For the new host 69.63.184.145,
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">
<scandiff>
<hostdiff>
<host>
<status state="up"/>
<address addr="69.63.178.41" addrtype="ipv4"/>
<hostnames>
<hostname name="photos-cache-snc1.facebook.com"/>
</hostnames>
<ports>
<extraports count="99" state="filtered"/>
<portdiff>
<port portid="80" protocol="tcp">
<state state="open"/>
<a>
<service name="http"/>
</a>
<b>
<service name="http" product="lighttpd" version="1.5.0"/>
</b>
</port>
</portdiff>
</ports>
</host>
</hostdiff>
<hostdiff>
<host>
<status state="up"/>
<address addr="69.63.179.25" addrtype="ipv4"/>
<hostnames>
<a>
<hostname name="cm.out.snc1.tfbnw.net"/>
</a>
<b>
<hostname name="mailout-snc1.facebook.com"/>
</b>
</hostnames>
<ports>
<extraports count="100" state="filtered"/>
</ports>
</host>
</hostdiff>
<hostdiff>
<b>
<host>
<status state="up"/>
<address addr="69.63.184.145" addrtype="ipv4"/>
<ports>
<extraports count="98" state="filtered"/>
<port portid="80" protocol="tcp">
<state state="open"/>
<service name="http" product="Apache httpd"
version="1.3.41.fb1"/>
</port>
<port portid="443" protocol="tcp">
<state state="open"/>
<service name="http" product="Apache httpd" tunnel="ssl"
version="1.3.41.fb1"/>
</port>
</ports>
</host>
</b>
</hostdiff>
</scandiff>
</nmapdiff>
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
#!/bin/sh
TARGETS="targets"
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-$date
echo
fi
echo "*** NMAP RESULTS ***"
cat scan-$date.nmap
ln -sf scan-$date.xml scan-prev.xml
If the script is saved as /root/scan-ndiff.sh, add the following
line to root's crontab:
0 12 * * * /root/scan-ndiff.sh
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 <dev@nmap.org>.
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 <david@bamsoftware.com>
Michael Pattrick <mpattrick@rhinovirus.org>
https://nmap.org/ndiff/
1. released
https://seclists.org/nmap-hackers/2000/315
This page is part of the nmap (a network scanner) project.
Information about the project can be found at ⟨http://nmap.org/⟩.
If you have a bug report for this manual page, send it to
dev@nmap.org. This page was obtained from the project's upstream
Git mirror of the Subversion repository
⟨https://github.com/nmap/nmap⟩ on 2023-12-22. (At that time, the
date of the most recent commit that was found in the repository
was 2023-12-14.) If you discover any rendering problems in this
HTML version of the page, or you believe there is a better or
more up-to-date source for the page, or you have corrections or
improvements to the information in this COLOPHON (which is not
part of the original manual page), send a mail to
man-pages@man7.org
Ndiff 05/17/2023 NDIFF(1)
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HTML rendering created 2023-12-22 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
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