Nast is a packet sniffer and a LAN analyzer based on Libnet and Libpcap.
It can sniff in normal mode or in promiscuous mode the packets on a network interface and log it.
It dumps the headers of packets and the payload in ascii or ascii-hex format.
You can apply a filter. The sniffed data can be saved in a separated file.
As analyzer tool, it has many features like:
* Build LAN hosts list
* Follow a TCP-DATA stream
* Find LAN Internet gateways
* Discover promiscuous nodes
* Reset an established connection
* Perform a single half-open portscanner
* Perform a multi half-open portscanner
* Find link type (hub or switch)
* Catch daemon banner of LAN nodes
* Control ARP answers to discover possible ARP-spoofing
* Byte counting with an optional filter
* Write reports logging
It also provides a new ncurses interface.
CMDLINE SNIFFER OPTIONS
-i, --interface
Select the Interface, if not specified will be auto-detected.
-p, --promisc
Disable promiscuous mode on NIC.
-d, --ascii-data
Print data in ascii format.
-x, --ascii-hex-data
Print data in ascii-hex format.
-f, --filter <"filter">
Apply <"filter"> to sniffer (see "FILTER SYNTAX" section below for syntax)
--ld <filename>
Log captured data to <filename> (only payload). Use -l to log all packet instead, useful with -B
-T, --tcpdump-log <filename>
Log all packets in tcpdump format to <filename>
-R, --tcpdump-log-read <filename>
Read all packets saved in tcpdump format from <filename>
ANALYZER FEATURES
-P, --check-promisc <ip>
Check other NIC on the LAN with the promiscuous flag set.
By performing a fake ARP broadcast, we can determine if a NIC is in promiscuous mode or not.
If the checked host is in promiscuous mode it will responds with an ARP response otherwise it drop the packet.
Note: This method doesn't work with all OS
Use -P all to query all network NIC
eg: root@localhost:~/$ nast -P 192.168.1.2
NAST "NETWORK ANALYZER SNIFFER TOOL"
192.168.1.2 (localhost.org) Found!!
We can check all nodes by using:
root@localhost:~/$ nast -P all
-m, --host-list
Map the LAN by performing a series of ARP request to sequential subnet IP
addresses.
eg: root@localhost:~/$ nast -m
NAST "NETWORK ANALYZER SNIFFER TOOL"
Mapping the Lan for 255.255.255.0 subnet ... please wait
MAC address IP address (hostname)
===========================================================
00:4R:BR:3E:21:12 192.168.1.1(nast.experiment.net)
00:50:BA:80:AC:11 192.168.1.2 (localhost.org) (*)
(*) This is localhost
-s, --tcp-stream
Follow a TCP/IP connection printing all data in payload. You must specify the IP addresses of the ends.
eg of a ftp connection:
root@localhost:~/$ nast -s
NAST "NETWORK ANALYZER SNIFFER TOOL"
Type connection extremes
------------------------
1st ip : 192.168.1.1
1st port : 1041
2nd : 192.168.1.2
2nd port : 21
Try to find possible Internet-gateways.
We send a SYN packet to a public host on port 80 through sequential host-lan and if a SYN-ACK
return we have find the gateway.
-r, --reset-connection
Destroy an established connection. You must specify the IP addresses of the ends and at least one port .
Please, pay attention when use this function.
eg: root@localhost:~/$ nast -r
NAST "NETWORK ANALYZER SNIFFER TOOL"
Type connection extremes
------------------------
1 ip / hostname : 192.168.1.1
1 port (0 to autodetect) : 0
2 ip / hostname : 192.168.1.2
2 port (0 to autodetect) : 21
- Waiting for SEQ ACK (192.168.1.1 -> 192.168.1.2:21)
- Stoled SEQ (247656261) ACK (3764364876)...
- Connection has been resetted
This feature works only if we can read SEQ and ACK numbers, because RST
mechanism works with them.
-S, --port-scanner
Performs a half-open port scanning on the selected host. It tries also to determine some firewall (just iptables) rules.
About this technique NMAP says:
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.
eg: root@localhost:~/$ nast -S
NAST "NETWORK ANALYZER SNIFFER TOOL"
Port Scanner extremes
Insert IP to scan : 192.168.1.3
Insert Port range : 1-100
Wait for scanning...
State Port Services Notes
Open 22 ssh None
Open 27 nsw-fe None
All the other 98 ports are in state closed
Scanning terminated on Apr 14 21:46:55
The Port range could be in the following style:
eg: 1-100 (means from port 1 to 100)
1,3,5,1000 (means ports 1,3,5 and 1000)
1-50,60 (means from port 1 to 50 and port 60)
-M, --multi-port-scanner
Same as above but done on all hosts of the lan.
-L, --find-link
Tries to determine what type of link is used in the LAN (Hub or switch).
In the LAN segment is there a HUB or a SWITCH? We can find it by sending a
spoofed ICMP echo-request (to work there must be at least 3 host in LAN and
at least one of them must reply with a ICMP echo-replay)
-b, --daemon-banner
Checks the most famous daemon banner on the LAN's hosts.
You can customize ports database adding them to ports[] variable in main.c
-c, --check-arp-poisoning
Control ARP answers to discover possible ARP spoofing attacks like
man-in-the-middle
When run, Nast make a database of all network node (IP and MAC address),
then sniff ARP response and verify the correctness of IP-mac address association.
Remember to execute Nast when you are sure that
nobody is making ARP-poisoning, than have fun and relax and check program output:).
-C, --byte-counting <"filter">
Apply traffic counting to <"filter"> (see FILTER SYNTAX section below for syntax)
Use -C any if you don't want to use a filter.
eg: root@localhost:~/$ nast -C any
NAST "NETWORK ANALYZER SNIFFER TOOL"
Reading from "eth0"
Packets Total Current speed Average speed
----------------------------------------------------------------
- 24 1008B 18B/s 21B/s
GENERAL OPTIONS
-G, --ncurses
Run Nast with the ncurses interfaces (only if compiled with ncurses support)
-l, --log-file <filename>
Log reports to <filename>. Work with many features.
-B, --daemon
Run in background like daemon and turn off stdout (very useful for sniffer/stream/ARP control logging)
-V, --version
Show version information
NCURSES INTERFACE NOTE
Versions later 0.2.0 have a new ncurses interface which has many improvements
regarding the correspondent command line version. For example you can select the
connection interactively for tcp stream and reset features and byte counting
module show much more informations (packets type and connections load).
Please read NCURSES_README file before using the ncurses interface!
FILTER SYNTAX, WHAT PCAP GIVE US!
Important: this section has been copied from Tcpdump 3.7.1 manpage
and "expression" here stand from "filter".
Remeber to enclose filter between apexes ("something like this")
"
selects which packets will be dumped.
If no expression
is given, all packets on the net will be dumped.
Otherwise,
only packets for which expression is `true' will be dumped.
The expression consists of one or more
primitives. Primitives usually consist of an
id (name or number) preceded by one or more qualifiers.
There are three
different kinds of qualifier:
type
qualifiers say what kind of thing the id name or number refers to.
Possible types are
host , net and
port . E.g., `host foo', `net 128.3', `port 20'.
If there is no type
qualifier,
host is assumed.
dir
qualifiers specify a particular transfer direction to and/or from
id . Possible directions are
src , dst , src or dst and
src and dst . E.g., `src foo', `dst net 128.3', `src or dst port ftp-data'.
If
there is no dir qualifier,
src or dst is assumed.
For `null' link layers (i.e. point to point protocols such as slip) the
inbound and
outbound qualifiers can be used to specify a desired direction.
proto
qualifiers restrict the match to a particular protocol.
Possible
protos are:
ether , fddi , tr , ip , ip6 , arp , rarp , decnet , tcp and
udp . E.g., `ether src foo', `arp net 128.3', `tcp port 21'.
If there is
no proto qualifier, all protocols consistent with the type are
assumed.
E.g., `src foo' means `(ip or arp or rarp) src foo'
(except the latter is not legal syntax), `net bar' means `(ip or
arp or rarp) net bar' and `port 53' means `(tcp or udp) port 53'.
[`fddi' is actually an alias for `ether'; the parser treats them
identically as meaning ``the data link level used on the specified
network interface.'' FDDI headers contain Ethernet-like source
and destination addresses, and often contain Ethernet-like packet
types, so you can filter on these FDDI fields just as with the
analogous Ethernet fields.
FDDI headers also contain other fields,
but you cannot name them explicitly in a filter expression.
Similarly, `tr' is an alias for `ether'; the previous paragraph's
statements about FDDI headers also apply to Token Ring headers.]
In addition to the above, there are some special `primitive' keywords
that don't follow the pattern:
gateway , broadcast , less , greater and arithmetic expressions.
All of these are described below.
More complex filter expressions are built up by using the words
and , or and
not to combine primitives.
E.g., `host foo and not port ftp and not port ftp-data'.
To save typing, identical qualifier lists can be omitted.
E.g.,
`tcp dst port ftp or ftp-data or domain' is exactly the same as
`tcp dst port ftp or tcp dst port ftp-data or tcp dst port domain'.
Allowable primitives are:
"dst
True if the IPv4/v6 destination field of the packet is host,
which may be either an address or a name.
"src
True if the IPv4/v6 source field of the packet is host.
"host host
True if either the IPv4/v6 source or destination of the packet is host.
Any of the above host expressions can be prepended with the keywords,
ip, arp, rarp, or ip6 as in:
ip host host
which is equivalent to:
ether proto \ip and host host
If host is a name with multiple IP addresses, each address will
be checked for a match.
"ether dst ehost
True if the ethernet destination address is ehost.
Ehost
may be either a name from /etc/ethers or a number (see
ethers (3N) for numeric format).
"ether src ehost
True if the ethernet source address is ehost.
"ether host ehost
True if either the ethernet source or destination address is ehost.
"gatewayhost
True if the packet used host as a gateway.
I.e., the ethernet
source or destination address was host but neither the IP source
nor the IP destination was host.
Host must be a name and
must be found both by the machine's host-name-to-IP-address resolution
mechanisms (host name file, DNS, NIS, etc.) and by the machine's
host-name-to-Ethernet-address resolution mechanism (/etc/ethers, etc.).
(An equivalent expression is
ether host ehost and not host host
which can be used with either names or numbers for host / ehost.)
This syntax does not work in IPv6-enabled configuration at this moment.
"dst
True if the IPv4/v6 destination address of the packet has a network
number of net.
Net may be either a name from /etc/networks
or a network number (see networks(4) for details).
"src
True if the IPv4/v6 source address of the packet has a network
number of net.
"net
True if either the IPv4/v6 source or destination address of the packet has a network
number of net.
"net
True if the IP address matches net with the specific netmask.
May be qualified with src or dst.
Note that this syntax is not valid for IPv6 net.
"net
True if the IPv4/v6 address matches net with a netmask len
bits wide.
May be qualified with src or dst.
"dst
True if the packet is ip/tcp, ip/udp, ip6/tcp or ip6/udp and has a
destination port value of port.
The port can be a number or a name used in /etc/services (see
tcp (4P) and
udp (4P)). If a name is used, both the port
number and protocol are checked.
If a number or ambiguous name is used,
only the port number is checked (e.g., dst port 513 will print both
tcp/login traffic and udp/who traffic, and port domain will print
both tcp/domain and udp/domain traffic).
"src
True if the packet has a source port value of port.
"port
True if either the source or destination port of the packet is port.
Any of the above port expressions can be prepended with the keywords,
tcp or udp, as in:
tcp src port port
which matches only tcp packets whose source port is port.
"less
True if the packet has a length less than or equal to length.
This is equivalent to:
len <= length.
"greater
True if the packet has a length greater than or equal to length.
This is equivalent to:
len >= length.
"ip
True if the packet is an IP packet (see
ip (4P)) of protocol type protocol.
Protocol can be a number or one of the names
icmp, icmp6, igmp, igrp, pim, ah,
esp, vrrp, udp, or tcp.
Note that the identifiers tcp, udp, and icmp are also
keywords and must be escaped via backslash (\), which is \\ in the C-shell.
Note that this primitive does not chase the protocol header chain.
"ip6
True if the packet is an IPv6 packet of protocol type protocol.
Note that this primitive does not chase the protocol header chain.
"ip6
True if the packet is IPv6 packet,
and contains protocol header with type protocol
in its protocol header chain.
For example,
ip6 protochain 6
matches any IPv6 packet with TCP protocol header in the protocol header chain.
The packet may contain, for example,
authentication header, routing header, or hop-by-hop option header,
between IPv6 header and TCP header.
The BPF code emitted by this primitive is complex and
cannot be optimized by BPF optimizer code in tcpdump,
so this can be somewhat slow.
"ip
Equivalent to ip6 protochain protocol, but this is for IPv4.
"ether
True if the packet is an ethernet broadcast packet.
The ether
keyword is optional.
"ip
True if the packet is an IP broadcast packet.
It checks for both
the all-zeroes and all-ones broadcast conventions, and looks up
the local subnet mask.
"ether
True if the packet is an ethernet multicast packet.
The ether
keyword is optional.
This is shorthand for `ether[0] & 1 != 0'.
"ip
True if the packet is an IP multicast packet.
"ip6
True if the packet is an IPv6 multicast packet.
True if the packet is of ether type protocol.
Protocol can be a number or one of the names
ip, ip6, arp, rarp, atalk, aarp,
decnet, sca, lat, mopdl, moprc,
iso, stp, ipx, or netbeui.
Note these identifiers are also keywords
and must be escaped via backslash (\).
[In the case of FDDI (e.g., `fddi protocol arp') and Token Ring
(e.g., `tr protocol arp'), for most of those protocols, the
protocol identification comes from the 802.2 Logical Link Control (LLC)
header, which is usually layered on top of the FDDI or Token Ring
header.
When filtering for most protocol identifiers on FDDI or Token Ring,
tcpdump checks only the protocol ID field of an LLC header in
so-called SNAP format with an Organizational Unit Identifier (OUI) of
0x000000, for encapsulated Ethernet; it doesn't check whether the packet
is in SNAP format with an OUI of 0x000000.
The exceptions are iso, for which it checks the DSAP (Destination
Service Access Point) and SSAP (Source Service Access Point) fields of
the LLC header, stp and netbeui, where it checks the DSAP of
the LLC header, and atalk, where it checks for a SNAP-format
packet with an OUI of 0x080007 and the Appletalk etype.
In the case of Ethernet, tcpdump checks the Ethernet type field
for most of those protocols; the exceptions are iso, sap,
and netbeui, for which it checks for an 802.3 frame and then
checks the LLC header as it does for FDDI and Token Ring, atalk,
where it checks both for the Appletalk etype in an Ethernet frame and
for a SNAP-format packet as it does for FDDI and Token Ring, aarp,
where it checks for the Appletalk ARP etype in either an Ethernet frame
or an 802.2 SNAP frame with an OUI of 0x000000, and ipx, where it
checks for the IPX etype in an Ethernet frame, the IPX DSAP in the LLC
header, the 802.3 with no LLC header encapsulation of IPX, and the IPX
etype in a SNAP frame.]
"decnet
True if the DECNET source address is
host , which may be an address of the form ``10.123'', or a DECNET host
name.
[DECNET host name support is only available on Ultrix systems
that are configured to run DECNET.]
"decnet
True if the DECNET destination address is
host .
"decnet
True if either the DECNET source or destination address is
host .
"ip,
Abbreviations for:
ether proto p
where p is one of the above protocols.
"lat,
Abbreviations for:
ether proto p
where p is one of the above protocols.
Note that
tcpdump does not currently know how to parse these protocols.
"vlan
True if the packet is an IEEE 802.1Q VLAN packet.
If [vlan_id] is specified, only true is the packet has the specified
vlan_id.
Note that the first vlan keyword encountered in expression
changes the decoding offsets for the remainder of expression
on the assumption that the packet is a VLAN packet.
Abbreviations for:
ip proto p or ip6 proto p
where p is one of the above protocols.
"iso
True if the packet is an OSI packet of protocol type protocol.
Protocol can be a number or one of the names
clnp, esis, or isis.
"clnp,
Abbreviations for:
iso proto p
where p is one of the above protocols.
Note that tcpdump does an incomplete job of parsing these protocols.
EXAMPLES
Here are some examples of the use of NAST:
nast -p -f "src 192.168.1.2"
In this example we put the NIC in promiscuous mode and with the help of the filter
we choose to see only the traffic from 192.168.1.2
nast -p -B --ld logfile.txt
Here we run nast in background mode and log all data that pass through our NIC.
nast -S -l logfile.txt
In this other case we log the results of the port scanner in the file "logfile.txt"
nast -c -B
This is a very useful options. We run in background mode nast that checks if someone
is arp-poisoning.
SUPPORTED PLATFORMS
Tested:
* Linux 2.4.x
* Linux 2.6.x
* FreeBSD 5.x
* FreeBSD 4.x
Not tested yet:
* Linux 2.2.x
AVAILABILITY
Official web site: http://nast.berlios.de
Newsletter: http://lists.berlios.de/mailman/listinfo/nast-news
KNOWN BUGS
* Promiscuous mode scanner many times returns wrong results
* Sometimes the port scanner generates false results
Please report bugs to authors
AUTHORS
Embyte <embyte@madlab.it>
Snifth <snifth@box.it>
LICENSE
GNU GENERAL PUBLIC LICENSE Version 2, June 1991
See COPYING for details.
