There is an old program a member of this online community made for everyone to use, but he is no longer around and no longer supports it. I wanted to help the community by extending it's features somewhat. To do that, I need to know how data is sent from it. How can I capture the network traffic it sends, and determine what it's sending?
WireShark is your friend. Available for UNIX and Windows.
Wireshark is a network packet analyzer. A network packet analyzer will
try to capture network packets and tries to display that packet data
as detailed as possible.
Wireshark User's Guide
#Kerrek SB's Tip: use tcpdump -s0 -w /tmp/data -i eth3 or so to create the dump file, and analyze it with Wireshark later as an unprivileged user.
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I need to exercise some hardware by sending a network traffic with it. While it is doing it I will probing some of the lines with an oscilloscope. Need to verify signaling. The problem is that I won't be able to connect to any server during the test. Many reasons for that, one of each is that hardware isn't complete yet.
Does anyone know if there is a away to generate network traffic with iperf without using a server? All I need is to just send some data, don't need to know if it was received. If there isn't can someone point me to a tool that can do that.
iperf UDP will do it you just need to make sure there is an arp entry for the destination (enter it manually) or use a multicast destination which doesn't require ARP, e.g. iperf -u -c 239.1.1.1 -b 10M
I am studying in traffic control and want to know how we can check packet dropped in a traffic control that I config it. Can we use ping icmp not?
You can use ping to check if there is currently some packet loss, but if you need to see if any packets were dropped before something like "netstat -s" or regularly checking the data in /proc/net/netstat (on unix-like systems) might be more useful.
How can I calculate the network utilization in terms of bytes transfered over the network card on the basis of its maximum potential speed? I am looking for something in unix/perl for unix os.
try the net-snmp package which implements the snmp protocol. theres an option to embed perl.
net-snmp
With this you can communicate with network devices and prompt for specific data they store. This data is pretty much standard for most devices although you will also find manufacturer's specifics. an example request for bytes transfered trough a port would be something like:
snmpwalk -Os -c public -v 1 192.168.1.2 ifInOctets.2
which will tell you the number of bytes passed trough the interface 2 on the device with the given address (192.168.1.2)
Also you might wanna check this tool for traffic monitoring, which is perl implementation.
mrtg
Another option on linux can be to use the /proc filesystem http://www.linuxjournal.com/article/8381
I'm trying to confirm a user a unplugged my embedded device from a network before performing some maintenance. I'm considering "ping"ing all IP address on my sub-net, but that sounds crude. Is there a broadcast/ARP method that might work better?
You can try a broadcast ping (this is from linux):
ping -b 255.255.255.255
Another option is to download Nmap and do a ping-scan.
You could use nmap. It's still crude, but at least it's using a tool designed to do it so you don't have to spend time on it.
If you can't get reliable link state information from your Ethernet device (which most chipsets should support these days, BTW...), sending an ARP request for each IP on your local subnet is a decent substitute. The overhead is minimal, and as soon as you get a single response, you can be sure you're still connected to a network.
The only possible problem I see here, is that if your device is on a /8 subnet, it can take quite a while to loop through all 4294967296 possible IPs. So, you may want to consider some optimization, such as only sending ARP requests for your default gateway, as well as all IPs currently in your ARP table.
If there's a peer you know you were connected to recently you could try pinging or arping that first. That could cut down on the traffic you're generating.
you could also run tcpdump -n to see what's active on the network too.
Not receiving any responses to ICMP pings or ARP requests is not a 100% guarantee that there's no network connection. For instances, there might be devices on the network that are firewalled off.
EDIT: May be you could access some lower-level information on your embedded device to check whether the network interface has its link up without actually sending any data.
Is there any chance that your device supports UPnP or Bonjour? Beside of the low-level protocols your should also have a look at these protocols which support some kind of plug-&-Play functionality. A UPnP device for example sends a message on the LAN before it is switched off (though, this doesn't help if it is just removed by unplugging it...).
How can I connect a system to a network and sniff for virus/spyware related traffic? I'd like to plug in a network cable, fire up an appropriate tool sand have it scan the data for any signs of problems. I don't expect this to find everything, and this is not to prevent initial infection but to help determine if there is anything trying to actively infect other system/causing network problems.
Running a regular network sniffer and manually looking through the results is no good unless the traffic is really obvious,but I havn't been able to find any tool to scan a network data stream automatically.
I highly recommend running Snort on a machine somewhere near the core of your network, and span (mirror) one (or more) ports from somewhere along your core network path to the machine in question.
Snort has the ability to scan network traffic it sees, and automatically notify you via various methods if it sees something suspicious. This could even be taken further, if desired, to automatically disconnect devices, et cetera, if it finds something.
Use snort: An open source network intrusion prevention and detection system.
Wireshark, formerly ethereal is a great tool, but will not notify you or scan for viruses. Wireshark is a free packet sniffer and protocol analyzer.
Use the netstat -b command to see which processes have which ports open.
Use CPorts to see a list of ports and the associated programs, and have the ability to close those ports.
Download a free anti-virus program such as free AVG.
Setup your firewall more tightly.
Setup a gateway computer to let all network traffic go through. Take the above recommendataions to the gateway computer instead. You will be checking your whole network instead of just your one computer.
You can make Snort scan traffic for viruses. I think this will be the best solution for you.
For watching local network traffic your best bet (with a decent switch) is to set your switch to route all packets out a specific interface (as well as whatever interface it would normally send). This lets you monitor the entire network by dumping traffic down a specific port.
On a 100 megabit network, however, you'll want a gigabit port on your switch to plug it into, or to filter on protocol (e.g. trim out HTTP, FTP, printing, traffic from the fileserver, etc.), or your switch's buffers are going to fill up pretty much instantly and it'll start dropping whatever packets it needs to (and your network performance will die).
The problem with that approach is that most networks today are on switches, not hubs. So, if you plug a machine with a packet sniffer into the switch, it will only be able to see traffic to and from the sniffing machine; and network broadcasts.
As a followup to Ferruccio's comment you will need to find some method of getting around your switches.
A number of network switches have the option of setting up port mirrors, so that all traffic (regardless of the destination) will be copied, or "mirrored", to a nominated port. If you could configure your switch to do this then you would be able to attach your network sniffer here.
Network Magic, if you don't mind something that's not open source.
You can use an IDS, hardware or software
http://en.wikipedia.org/wiki/Intrusion-detection_system