Last login: Sun Nov 24 03:10:44 on ttyp1 Welcome to Darwin! [Uisce:~] mcarroll% ssh red.ils.unc.edu mcarroll@red.ils.unc.edu's password: Last login: Sat Nov 23 17:36:24 2002 from rdu57-242-138.nc.rr.com [mcarroll@red mcarroll]$ nmap -sF 66.57.242.138 Starting nmap V. 3.00 ( www.insecure.org/nmap/ ) You requested a scan type which requires r00t privileges, and you do not have them. QUITTING! [mcarroll@red mcarroll]$ sudo nmap -sF 66.57.242.138 Password: Starting nmap V. 3.00 ( www.insecure.org/nmap/ ) Note: Host seems down. If it is really up, but blocking our ping probes, try -P0 Nmap run completed -- 1 IP address (0 hosts up) scanned in 30 seconds [mcarroll@red mcarroll]$ sudo nmap -sP 66.57.242.138 Starting nmap V. 3.00 ( www.insecure.org/nmap/ ) Note: Host seems down. If it is really up, but blocking our ping probes, try -P0 Nmap run completed -- 1 IP address (0 hosts up) scanned in 30 seconds [mcarroll@red mcarroll]$ nmap -sF 66.57.242.132 Starting nmap V. 3.00 ( www.insecure.org/nmap/ ) You requested a scan type which requires r00t privileges, and you do not have them. QUITTING! [mcarroll@red mcarroll]$ sudo nmap -sF 66.57.242.132 Starting nmap V. 3.00 ( www.insecure.org/nmap/ ) Interesting ports on rdu57-242-132.nc.rr.com (66.57.242.132): (The 1596 ports scanned but not shown below are in state: closed) Port State Service 69/tcp filtered tftp 137/tcp open netbios-ns 138/tcp open netbios-dgm 139/tcp open netbios-ssn 445/tcp open microsoft-ds Nmap run completed -- 1 IP address (1 host up) scanned in 16 seconds [mcarroll@red mcarroll]$ echo this is a neighbor!man nmap echo this is a neighborman nmap nmap this is a neighborman nmap nmap [mcarroll@red mcarroll]$ man nmap NMAP(1) NMAP(1) NAME nmap - Network exploration tool and security scanner NAME nmap - Network exploration tool and security scanner SYNOPSIS nmap [Scan Type(s)] [Options] DESCRIPTION Nmap is designed to allow system administrators and curious individuals to scan large networks to determine which hosts are up and what services they are offering. nmap supports a large number of scanning techniques such as: UDP, TCP connect(), TCP SYN (half open), ftp proxy (bounce attack), Reverse-ident, ICMP (ping sweep), FIN, ACK sweep, Xmas Tree, SYN sweep, IP Protocol, and Null scan. See the Scan Types section for more details. nmap also offers a number of advanced features such as remote OS detection via TCP/IP fingerprinting, stealth scanning, dynamic delay and retransmis- sion calculations, parallel scanning, detection of down hosts via parallel pings, decoy scanning, port filtering detection, direct (non-portmapper) RPC scanning, fragmentation scanning, and flexible target and port specifi- cation. Significant effort has been put into decent nmap performance for non-root users. Unfortunately, many critical kernel interfaces (such as raw sock- ets) require root privileges. nmap should be run as root whenever possible (not setuid root, of course). The result of running nmap is usually a list of interesting ports on the machine(s) being scanned (if any). Nmap always gives the port's "well known" service name (if any), number, state, and protocol. The state is either 'open', 'filtered', or 'unfiltered'. Open means that the target machine will accept() connections on that port. Filtered means that a firewall, filter, or other network obstacle is covering the port and pre- venting nmap from determining whether the port is open. Unfiltered means that the port is known by nmap to be closed and no firewall/filter seems to be interfering with nmap's attempts to determine this. Unfiltered ports are the common case and are only shown when most of the scanned ports are in the filtered state. Depending on options used, nmap may also report the following characteris- tics of the remote host: OS in use, TCP sequencability, usernames running the programs which have bound to each port, the DNS name, whether the host is a smurf address, and a few others. OPTIONS Options that make sense together can generally be combined. Some options are specific to certain scan modes. nmap tries to catch and warn the user about psychotic or unsupported option combinations. If you are impatient, you can skip to the examples section at the end, which demonstrates common usage. You can also run nmap -h for a quick ref- erence page listing all the options. SCAN TYPES -sS TCP SYN scan: This technique is often referred to as "half-open" scanning, because you don't open a full TCP connection. You send a SYN packet, as if you are going to open a real connection and you wait for a response. A SYN|ACK indicates the port is listening. A RST is indicative of a non-listener. If a SYN|ACK is received, a RST is immediately sent to tear down the connection (actually our OS kernel does this for us). The primary advantage to this scanning technique is that fewer sites will log it. Unfortunately you need root privileges to build these custom SYN packets. This is the default scan type for privileged users. -sT TCP connect() scan: This is the most basic form of TCP scanning. The connect() system call provided by your operating system is used to open a connection to every interesting port on the machine. If the port is listening, connect() will succeed, otherwise the port isn't reachable. One strong advantage to this technique is that you don't need any special privileges. Any user on most UNIX boxes is free to use this call. This sort of scan is easily detectable as target host logs will show a bunch of connection and error messages for the services which accept() the connection just to have it immediately shutdown. This is the default scan type for unprivileged users. -sF -sX -sN Stealth FIN, Xmas Tree, or Null scan modes: There are times when even SYN scanning isn't clandestine enough. Some firewalls and packet filters watch for SYNs to restricted ports, and programs like Synlogger and Courtney are available to detect these scans. These advanced scans, on the other hand, may be able to pass through unmo- lested. The idea is that closed ports are required to reply to your probe packet with an RST, while open ports must ignore the packets in question (see RFC 793 pp 64). The FIN scan uses a bare (surprise) FIN packet as the probe, while the Xmas tree scan turns on the FIN, URG, and PUSH flags. The Null scan turns off all flags. Unfortu- nately Microsoft (like usual) decided to completely ignore the stan- dard and do things their own way. Thus this scan type will not work against systems running Windows95/NT. On the positive side, this is a good way to distinguish between the two platforms. If the scan finds open ports, you know the machine is not a Windows box. If a -sF,-sX,or -sN scan shows all ports closed, yet a SYN (-sS) scan shows ports being opened, you are probably looking at a Windows box. This is less useful now that nmap has proper OS detection built in. There are also a few other systems that are broken in the same way Windows is. They include Cisco, BSDI, HP/UX, MVS, and IRIX. All of the above send resets from the open ports when they should just drop the packet. -sP Ping scanning: Sometimes you only want to know which hosts on a net- work are up. Nmap can do this by sending ICMP echo request packets to every IP address on the networks you specify. Hosts that respond are up. Unfortunately, some sites such as microsoft.com block echo request packets. Thus nmap can also send a TCP ack packet to (by default) port 80. If we get an RST back, that machine is up. A third technique involves sending a SYN packet and waiting for a RST or a SYN/ACK. For non-root users, a connect() method is used. By default (for root users), nmap uses both the ICMP and ACK tech- niques in parallel. You can change the -P option described later. Note that pinging is done by default anyway, and only hosts that respond are scanned. Only use this option if you wish to ping sweep without doing any actual port scans. -sU UDP scans: This method is used to determine which UDP (User Datagram Protocol, RFC 768) ports are open on a host. The technique is to send 0 byte udp packets to each port on the target machine. If we receive an ICMP port unreachable message, then the port is closed. Otherwise we assume it is open. Some people think UDP scanning is pointless. I usually remind them of the recent Solaris rcpbind hole. Rpcbind can be found hiding on an undocumented UDP port somewhere above 32770. So it doesn't matter that 111 is blocked by the firewall. But can you find which of the more than 30,000 high ports it is listening on? With a UDP scanner you can! There is also the cDc Back Orifice backdoor program which hides on a configurable UDP port on Windows machines. Not to men- tion the many commonly vulnerable services that utilize UDP such as snmp, tftp, NFS, etc. Unfortunately UDP scanning is sometimes painfully slow since most hosts implement a suggestion in RFC 1812 (section 4.3.2.8) of limit- ing the ICMP error message rate. For example, the Linux kernel (in net/ipv4/icmp.h) limits destination unreachable message generation to 80 per 4 seconds, with a 1/4 second penalty if that is exceeded. Solaris has much more strict limits (about 2 messages per second) and thus takes even longer to scan. nmap detects this rate limiting and slows down accordingly, rather than flood the network with use- less packets that will be ignored by the target machine. As is typical, Microsoft ignored the suggestion of the RFC and does not seem to do any rate limiting at all on Win95 and NT machines. Thus we can scan all 65K ports of a Windows machine very quickly. Woop! -sO IP protocol scans: This method is used to determine which IP proto- cols are supported on a host. The technique is to send raw IP pack- ets without any further protocol header to each specified protocol on the target machine. If we receive an ICMP protocol unreachable message, then the protocol is not in use. Otherwise we assume it is open. Note that some hosts (AIX, HP-UX, Digital UNIX) and firewalls may not send protocol unreachable messages. This causes all of the protocols to appear "open". Because the implemented technique is very similar to UDP port scan- ning, ICMP rate limit might apply too. But the IP protocol field has only 8 bits, so at most 256 protocols can be probed which should be possible in reasonable time anyway. -sI Idlescan: This advanced scan method allows for a truly blind TCP port scan of the target (meaning no packets are sent to the target from your real IP address). Instead, a unique side-channel attack exploits predictable "IP fragmentation ID" sequence generation on the zombie host to glean information about the open ports on the target. IDS systems will display the scan as coming from the zombie machine you specify (which must be up and meet certain criteria). I am planning to put a more detailed explanation up at http://www.insecure.org/nmap/nmap_documentation.html in the near future. Besides being extraordinarily stealthy (due to its blind nature), this scan type permits mapping out IP-based trust relationships between machines. The port listing shows open ports from the per- spective of the zombie host. So you can try scanning a target using various zombies that you think might be trusted (via router/packet filter rules). Obviously this is crucial information when priori- tizing attack targets. Otherwise, you penetration testers might have to expend considerable resources "owning" an intermediate sys- tem, only to find out that its IP isn't even trusted by the target host/network you are ultimately after. You can add a colon followed by a port number if you wish to probe a particular port on the zombie host for IPID changes. Otherwise Nmap will use the port it uses by default for "tcp pings". -sA ACK scan: This advanced method is usually used to map out firewall rulesets. In particular, it can help determine whether a firewall is stateful or just a simple packet filter that blocks incoming SYN packets. This scan type sends an ACK packet (with random looking acknowledge- ment/sequence numbers) to the ports specified. If a RST comes back, the ports is classified as "unfiltered". If nothing comes back (or if an ICMP unreachable is returned), the port is classified as "fil- tered". Note that nmap usually doesn't print "unfiltered" ports, so getting no ports shown in the output is usually a sign that all the probes got through (and returned RSTs). This scan will obviously never show ports in the "open" state. -sW Window scan: This advanced scan is very similar to the ACK scan, except that it can sometimes detect open ports as well as fil- tered/nonfiltered due to an anomaly in the TCP window size reporting by some operating systems. Systems vulnerable to this include at least some versions of AIX, Amiga, BeOS, BSDI, Cray, Tru64 UNIX, DG/UX, OpenVMS, Digital UNIX, FreeBSD, HP-UX, OS/2, IRIX, MacOS, NetBSD, OpenBSD, OpenStep, QNX, Rhapsody, SunOS 4.X, Ultrix, VAX, and VxWorks. See the nmap-hackers mailing list archive for a full list. -sR RPC scan. This method works in combination with the various port scan methods of Nmap. It takes all the TCP/UDP ports found open and then floods them with SunRPC program NULL commands in an attempt to determine whether they are RPC ports, and if so, what program and version number they serve up. Thus you can effectively obtain the same info as firewall (or protected by TCP wrappers). Decoys do not currently work with RPC scan, at some point I may add decoy support for UDP RPC scans. -sL List scan. This method simply generates and prints a list of IPs/Names without actually pinging or port scanning them. DNS name resolution will be performed unless you use -n. -b FTP bounce attack: An interesting "feature" of the ftp protocol (RFC 959) is support for "proxy" ftp connections. In other words, I should be able to connect from evil.com to the FTP server of tar- get.com and request that the server send a file ANYWHERE on the internet! Now this may have worked well in 1985 when the RFC was written. But in today's Internet, we can't have people hijacking ftp servers and requesting that data be spit out to arbitrary points on the internet. As *Hobbit* wrote back in 1995, this protocol flaw "can be used to post virtually untraceable mail and news, hammer on servers at various sites, fill up disks, try to hop firewalls, and generally be annoying and hard to track down at the same time." What we will exploit this for is to (surprise, surprise) scan TCP ports from a "proxy" ftp server. Thus you could connect to an ftp server behind a firewall, and then scan ports that are more likely to be blocked (139 is a good one). If the ftp server allows reading from and writing to some directory (such as /incoming), you can send arbitrary data to ports that you do find open (nmap doesn't do this for you though). The argument passed to the 'b' option is the host you want to use as a proxy, in standard URL notation. The format is: username:pass- word@server:port. Everything but server is optional. To determine what servers are vulnerable to this attack, you can see my article in Phrack 51. And updated version is available at the nmap URL (http://www.insecure.org/nmap). GENERAL OPTIONS None of these are required but some can be quite useful. -P0 Do not try and ping hosts at all before scanning them. This allows the scanning of networks that don't allow ICMP echo requests (or responses) through their firewall. microsoft.com is an example of such a network, and thus you should always use -P0 or -PT80 when portscanning microsoft.com. -PT Use TCP "ping" to determine what hosts are up. Instead of sending ICMP echo request packets and waiting for a response, we spew out TCP ACK packets throughout the target network (or to a single machine) and then wait for responses to trickle back. Hosts that are up should respond with a RST. This option preserves the effi- ciency of only scanning hosts that are up while still allowing you to scan networks/hosts that block ping packets. For non root users, we use connect(). To set the destination port of the probe packets use -PT. The default port is 80, since this port is often not filtered out. -PS This option uses SYN (connection request) packets instead of ACK packets for root users. Hosts that are up should respond with a RST (or, rarely, a SYN|ACK). You can set the destination port in the same manner as -PT above. -PI This option uses a true ping (ICMP echo request) packet. It finds hosts that are up and also looks for subnet-directed broadcast addresses on your network. These are IP addresses which are exter- nally reachable and translate to a broadcast of incomming IP packets to a subnet of computers. These should be eliminated if found as they allow for numerous denial of service attacks (Smurf is the most common). -PP Uses an ICMP timestamp request (code 13) packet to find listening hosts. -PM Same as -PI and -PP except uses a netmask request (ICMP code 17). -PB This is the default ping type. It uses both the ACK ( -PT ) and ICMP echo request ( -PI ) sweeps in parallel. This way you can get firewalls that filter either one (but not both). The TCP probe des- tination port can be set in the same manner as with -PT above. -O This option activates remote host identification via TCP/IP finger- printing. In other words, it uses a bunch of techniques to detect subtleties in the underlying operating system network stack of the computers you are scanning. It uses this information to create a firewalls that filter either one (but not both). The TCP probe des- tination port can be set in the same manner as with -PT above. -O This option activates remote host identification via TCP/IP finger- printing. In other words, it uses a bunch of techniques to detect subtleties in the underlying operating system network stack of the computers you are scanning. It uses this information to create a 'fingerprint' which it compares with its database of known OS fin- gerprints (the nmap-os-fingerprints file) to decide what type of system you are scanning. If Nmap is unable to guess the OS of a machine, and conditions are good (eg at least one open port), Nmap will provide a URL you can use to submit the fingerprint if you know (for sure) the OS running on the machine. By doing this you contribute to the pool of operat- ing systems known to nmap and thus it will be more accurate for everyone. Note that if you leave an IP address on the form, the machine may be scanned when we add the fingerprint (to validate that it works). The -O option also enables several other tests. One is the "Uptime" measurement, which uses the TCP timestamp option (RFC 1323) to guess when a machine was last rebooted. This is only reported for machines which provide this information. Another test enabled by -O is TCP Sequence Predictability Classifi- cation. This is a measure that describes approximately how hard it is to establish a forged TCP connection against the remote host. This is useful for exploiting source-IP based trust relationships (rlogin, firewall filters, etc) or for hiding the source of an attack. The actual difficulty number is based on statistical sam- pling and may fluctuate. It is generally better to use the English classification such as "worthy challenge" or "trivial joke". This is only reported in normal output with -v. [mcarroll@red mcarroll]$ sudo nmap -sA -O 66.57.242.138 Password: Starting nmap V. 3.00 ( www.insecure.org/nmap/ ) Note: Host seems down. If it is really up, but blocking our ping probes, try -P0 Nmap run completed -- 1 IP address (0 hosts up) scanned in 30 seconds [mcarroll@red mcarroll]$ sudo nmap -sA -O 66.57.242.132 Starting nmap V. 3.00 ( www.insecure.org/nmap/ ) Warning: OS detection will be MUCH less reliable because we did not find at least 1 open and 1 closed TCP port Interesting ports on rdu57-242-132.nc.rr.com (66.57.242.132): (The 1596 ports scanned but not shown below are in state: UNfiltered) Port State Service 69/tcp filtered tftp 137/tcp filtered netbios-ns 138/tcp filtered netbios-dgm 139/tcp filtered netbios-ssn 445/tcp filtered microsoft-ds Too many fingerprints match this host for me to give an accurate OS guess Nmap run completed -- 1 IP address (1 host up) scanned in 31 seconds [mcarroll@red mcarroll]$ sudo nmap -sA -O -P0 66.57.242.132 Starting nmap V. 3.00 ( www.insecure.org/nmap/ ) Warning: OS detection will be MUCH less reliable because we did not find at least 1 open and 1 closed TCP port Interesting ports on rdu57-242-132.nc.rr.com (66.57.242.132): (The 1596 ports scanned but not shown below are in state: UNfiltered) Port State Service 69/tcp filtered tftp 137/tcp filtered netbios-ns 138/tcp filtered netbios-dgm 139/tcp filtered netbios-ssn 445/tcp filtered microsoft-ds Too many fingerprints match this host for me to give an accurate OS guess Nmap run completed -- 1 IP address (1 host up) scanned in 31 seconds [mcarroll@red mcarroll]$ sudo nmap -sA -O -P0 66.57.242.138 Starting nmap V. 3.00 ( www.insecure.org/nmap/ ) qcaught SIGINT signal, cleaning up [mcarroll@red mcarroll]$ finger 66.57.242.138 finger: 66.57.242.138: no such user. [mcarroll@red mcarroll]$