Adam Palmer MBCS CITP, Linux, PHP Programmer, MySQL Developer, Embedded Hardware, Security Consultant
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02 Sep 09 Security Consultant – Basic NMAP Usage
nmap is one of the most useful tools for a security consultant in a penetration testing environment. It has a massive range of options, and only the most basic will be considered in this tutorial.
It goes without saying, that nmap should only be run against IPs and ports that you yourself have gained authorization to test. Here goes:
We’ll be testing an IP address of 192.168.1.1 in our examples. The key options that we’re interested in are -T, -s, -n, -O and -p.
The -s option specifies the type of scan, and -p specifies the port(ranges).
nmap -sT 192.168.1.1
Performs a TCP scan against standard ports with default options
nmap -sU -p 5,7,9,100-150,250,300 192.168.1.1
Performs a UDP scan again ports 5, 7, 9, 100 to 150 inclusive, 250 and 300
nmap -sP 192.168.1-2.1-254
Perform a ping scan of 192.168.1.1 to 192.168.2.254 inclusive (254 * 2 = 508 hosts)
nmap -sT -O 192.168.1.1
Perform a standard TCP Scan AND OS fingerprint of the host. How OS fingerprinting works is outside of the scope of this article, however assuming at least one open and one closed (not dropped) port is found, OS detection is usually reliable.
nmap -Tinsane -sT -p1-65535
Use ‘insane’ fast timing when scanning and scan all 1 to 65535 TCP ports
nmap -Taggressive -sU -p1-65535 -n
Use ‘aggressive’ fast timing when scanning, scan all 1 to 65535 UDP ports and do not attempt to resolve 192.168.1.1 to a hostname
nmap -sO 192.168.1.1 -n
Scan for IP Protocols, and do not attempt to resolve 192.168.1.1 to a hostname. Sample Output:
Not shown: 250 closed protocols PROTOCOL STATE SERVICE 1 open icmp 2 open|filtered igmp 6 open tcp 17 open udp 136 open|filtered udplite 255 open|filtered unknown
nmap -O -sV -p21,110,123 192.168.1.1
Scan 192.168.1.1 and attempt to gain banner/server information from services running on ports 21, 110 and 123. We’ll include 123 which we know to be closed so that nmap can use the closed port in the OS scan. Sample Output:
PORT STATE SERVICE VERSION 21/tcp open ftp vsftpd 2.0.7 110/tcp open pop3 Courier pop3d 123/tcp closed ntp Device type: general purpose Running: Linux 2.6.X OS details: Linux 2.6.18, Linux 2.6.20 - 2.6.24 Uptime: 65.658 days (since Mon Jun 29 00:43:29 2009) Network Distance: 0 hops Service Info: OS: Unix
nmap has plenty more powerful options, specifically useful when testing socket software, however the basics above are more than enough to be getting on with. Looking at nmap’s usage banner below, other options available mainly include timing, port ordering, firewall/IDS avoidance, and IP/Ethernet Packet/Frame header mangling.
ns3:~# nmap
Nmap 4.62 ( http://nmap.org )
Usage: nmap [Scan Type(s)] [Options] {target specification}
TARGET SPECIFICATION:
Can pass hostnames, IP addresses, networks, etc.
Ex: scanme.nmap.org, microsoft.com/24, 192.168.0.1; 10.0.0-255.1-254
-iL : Input from list of hosts/networks
-iR : Choose random targets
--exclude : Exclude hosts/networks
--excludefile : Exclude list from file
HOST DISCOVERY:
-sL: List Scan - simply list targets to scan
-sP: Ping Scan - go no further than determining if host is online
-PN: Treat all hosts as online -- skip host discovery
-PS/PA/PU [portlist]: TCP SYN/ACK or UDP discovery to given ports
-PE/PP/PM: ICMP echo, timestamp, and netmask request discovery probes
-PO [protocol list]: IP Protocol Ping
-n/-R: Never do DNS resolution/Always resolve [default: sometimes]
--dns-servers : Specify custom DNS servers
--system-dns: Use OS's DNS resolver
SCAN TECHNIQUES:
-sS/sT/sA/sW/sM: TCP SYN/Connect()/ACK/Window/Maimon scans
-sU: UDP Scan
-sN/sF/sX: TCP Null, FIN, and Xmas scans
--scanflags : Customize TCP scan flags
-sI : Idle scan
-sO: IP protocol scan
-b : FTP bounce scan
--traceroute: Trace hop path to each host
--reason: Display the reason a port is in a particular state
PORT SPECIFICATION AND SCAN ORDER:
-p
: Only scan specified ports
Ex: -p22; -p1-65535; -p U:53,111,137,T:21-25,80,139,8080
-F: Fast mode - Scan fewer ports than the default scan
-r: Scan ports consecutively - don't randomize
--top-ports : Scan most common ports
--port-ratio : Scan ports more common than
SERVICE/VERSION DETECTION:
-sV: Probe open ports to determine service/version info
--version-intensity : Set from 0 (light) to 9 (try all probes)
--version-light: Limit to most likely probes (intensity 2)
--version-all: Try every single probe (intensity 9)
--version-trace: Show detailed version scan activity (for debugging)
SCRIPT SCAN:
-sC: equivalent to --script=safe,intrusive
--script=: is a comma separated list of
directories, script-files or script-categories
--script-args=: provide arguments to scripts
--script-trace: Show all data sent and received
--script-updatedb: Update the script database.
OS DETECTION:
-O: Enable OS detection
--osscan-limit: Limit OS detection to promising targets
--osscan-guess: Guess OS more aggressively
TIMING AND PERFORMANCE:
Options which take are in milliseconds, unless you append 's'
(seconds), 'm' (minutes), or 'h' (hours) to the value (e.g. 30m).
-T[0-5]: Set timing template (higher is faster)
--min-hostgroup/max-hostgroup : Parallel host scan group sizes
--min-parallelism/max-parallelism : Probe parallelization
--min-rtt-timeout/max-rtt-timeout/initial-rtt-timeout : Specifies
probe round trip time.
--max-retries
: Caps number of port scan probe retransmissions.
--host-timeout : Give up on target after this long
--scan-delay/--max-scan-delay : Adjust delay between probes
--min-rate : Send packets no slower than per second
FIREWALL/IDS EVASION AND SPOOFING:
-f; --mtu : fragment packets (optionally w/given MTU)
-D : Cloak a scan with decoys
-S : Spoof source address
-e : Use specified interface
-g/--source-port
: Use given port number
--data-length : Append random data to sent packets
--ip-options : Send packets with specified ip options
--ttl : Set IP time-to-live field
--spoof-mac : Spoof your MAC address
--badsum: Send packets with a bogus TCP/UDP checksum
OUTPUT:
-oN/-oX/-oS/-oG : Output scan in normal, XML, s|: Output in the three major formats at once
-v: Increase verbosity level (use twice or more for greater effect)
-d[level]: Set or increase debugging level (Up to 9 is meaningful)
--open: Only show open (or possibly open) ports
--packet-trace: Show all packets sent and received
--iflist: Print host interfaces and routes (for debugging)
--log-errors: Log errors/warnings to the normal-format output file
--append-output: Append to rather than clobber specified output files
--resume : Resume an aborted scan
--stylesheet
: XSL stylesheet to transform XML output to HTML
--webxml: Reference stylesheet from Insecure.Org for more portable XML
--no-stylesheet: Prevent associating of XSL stylesheet w/XML output
MISC:
-6: Enable IPv6 scanning
-A: Enables OS detection and Version detection, Script scanning and Traceroute
--datadir : Specify custom Nmap data file location
--send-eth/--send-ip: Send using raw ethernet frames or IP packets
--privileged: Assume that the user is fully privileged
--unprivileged: Assume the user lacks raw socket privileges
-V: Print version number
-h: Print this help summary page.
EXAMPLES:
nmap -v -A scanme.nmap.org
nmap -v -sP 192.168.0.0/16 10.0.0.0/8
nmap -v -iR 10000 -PN -p 80
SEE THE MAN PAGE FOR MANY MORE OPTIONS, DESCRIPTIONS, AND EXAMPLES
ns3:~# nmap
Nmap 4.62 ( http://nmap.org )
Usage: nmap [Scan Type(s)] [Options] {target specification}
TARGET SPECIFICATION:
Can pass hostnames, IP addresses, networks, etc.
Ex: scanme.nmap.org, microsoft.com/24, 192.168.0.1; 10.0.0-255.1-254
-iL : Input from list of hosts/networks
-iR : Choose random targets
--exclude : Exclude hosts/networks
--excludefile : Exclude list from file
HOST DISCOVERY:
-sL: List Scan - simply list targets to scan
-sP: Ping Scan - go no further than determining if host is online
-PN: Treat all hosts as online -- skip host discovery
-PS/PA/PU [portlist]: TCP SYN/ACK or UDP discovery to given ports
-PE/PP/PM: ICMP echo, timestamp, and netmask request discovery probes
-PO [protocol list]: IP Protocol Ping
-n/-R: Never do DNS resolution/Always resolve [default: sometimes]
--dns-servers : Specify custom DNS servers
--system-dns: Use OS's DNS resolver
SCAN TECHNIQUES:
-sS/sT/sA/sW/sM: TCP SYN/Connect()/ACK/Window/Maimon scans
-sU: UDP Scan
-sN/sF/sX: TCP Null, FIN, and Xmas scans
--scanflags : Customize TCP scan flags
-sI : Idle scan
-sO: IP protocol scan
-b : FTP bounce scan
--traceroute: Trace hop path to each host
--reason: Display the reason a port is in a particular state
PORT SPECIFICATION AND SCAN ORDER:
-p
: Only scan specified ports
Ex: -p22; -p1-65535; -p U:53,111,137,T:21-25,80,139,8080
-F: Fast mode - Scan fewer ports than the default scan
-r: Scan ports consecutively - don't randomize
--top-ports : Scan most common ports
--port-ratio : Scan ports more common than
SERVICE/VERSION DETECTION:
-sV: Probe open ports to determine service/version info
--version-intensity : Set from 0 (light) to 9 (try all probes)
--version-light: Limit to most likely probes (intensity 2)
--version-all: Try every single probe (intensity 9)
--version-trace: Show detailed version scan activity (for debugging)
SCRIPT SCAN:
-sC: equivalent to --script=safe,intrusive
--script=: is a comma separated list of
directories, script-files or script-categories
--script-args=: provide arguments to scripts
--script-trace: Show all data sent and received
--script-updatedb: Update the script database.
OS DETECTION:
-O: Enable OS detection
--osscan-limit: Limit OS detection to promising targets
--osscan-guess: Guess OS more aggressively
TIMING AND PERFORMANCE:
Options which take are in milliseconds, unless you append 's'
(seconds), 'm' (minutes), or 'h' (hours) to the value (e.g. 30m).
-T[0-5]: Set timing template (higher is faster)
--min-hostgroup/max-hostgroup : Parallel host scan group sizes
--min-parallelism/max-parallelism : Probe parallelization
--min-rtt-timeout/max-rtt-timeout/initial-rtt-timeout : Specifies
probe round trip time.
--max-retries
: Caps number of port scan probe retransmissions.
--host-timeout : Give up on target after this long
--scan-delay/--max-scan-delay : Adjust delay between probes
--min-rate : Send packets no slower than per second
FIREWALL/IDS EVASION AND SPOOFING:
-f; --mtu : fragment packets (optionally w/given MTU)
-D : Cloak a scan with decoys
-S : Spoof source address
-e : Use specified interface
-g/--source-port
: Use given port number
--data-length : Append random data to sent packets
--ip-options : Send packets with specified ip options
--ttl : Set IP time-to-live field
--spoof-mac : Spoof your MAC address
--badsum: Send packets with a bogus TCP/UDP checksum
OUTPUT:
-oN/-oX/-oS/-oG : Output scan in normal, XML, s|: Output in the three major formats at once
-v: Increase verbosity level (use twice or more for greater effect)
-d[level]: Set or increase debugging level (Up to 9 is meaningful)
--open: Only show open (or possibly open) ports
--packet-trace: Show all packets sent and received
--iflist: Print host interfaces and routes (for debugging)
--log-errors: Log errors/warnings to the normal-format output file
--append-output: Append to rather than clobber specified output files
--resume : Resume an aborted scan
--stylesheet
: XSL stylesheet to transform XML output to HTML
--webxml: Reference stylesheet from Insecure.Org for more portable XML
--no-stylesheet: Prevent associating of XSL stylesheet w/XML output
MISC:
-6: Enable IPv6 scanning
-A: Enables OS detection and Version detection, Script scanning and Traceroute
--datadir : Specify custom Nmap data file location
--send-eth/--send-ip: Send using raw ethernet frames or IP packets
--privileged: Assume that the user is fully privileged
--unprivileged: Assume the user lacks raw socket privileges
-V: Print version number
-h: Print this help summary page.
EXAMPLES:
nmap -v -A scanme.nmap.org
nmap -v -sP 192.168.0.0/16 10.0.0.0/8
nmap -v -iR 10000 -PN -p 80
SEE THE MAN PAGE FOR MANY MORE OPTIONS, DESCRIPTIONS, AND EXAMPLES
Tags: daemon, ethernet, firewall, frame, ftp, header, ids, IP, mangle, nmap, paket, pen test, pen testing, penetration testing, POP3, port, security, Security Consultant, security consulting, socket, tcp, timing, udp
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I'm Adam Palmer, and I'm a Freelance Embedded Linux/Embedded Hardware enthusiast and Security Consultant. I run 'APNIC Solutions Ltd' and spend most of my time managing server clusters, and doing some PHP/MySQL development, whilst what little spare time I have is dedicated to playing with gadgets. I'm always happy to consult on or manage any Linux related, Web Application or Hosting project. Please get in touch with me! |
[...] here: Security Consultant – Basic NMAP Usage | Adam's Tech Talk, Linux … Posted in: [...]
[...] The first angle has to be the network security itself, all the way down the the physical security. As a penetration tester, I’ll test the web, database, storage and any other related networked devices inside and out. Port scanning their interfaces, spoofing IPs and MACs, asking myself questions such as “Does the database accept direct connections from any IP? Does Apache keep too many spare threads waiting?” We need to work our way from bottom to top of the OSI Model, a lot of which can be done using nc (Netcat) and a combination of scripts, as well as nmap. [...]