I have a small home network that I would like to analyze and capture the traffic on. What are my options for doing this? Ultimately, I would like to use a packet capture library, such as libpcap, to sniff the network in real-time as my router receives packets. I'm mainly interested in HTTP traffic. Thus far, when I run my program, I only seem to be able to see packets sourced or destined to my machine. Is there a way that I may inspect any traffic that travels through my wireless modem/router?
From the research I've done, it seems that the only way this is possible is through ARP poisoning or using a CISCO router that features Embedded Packet Capture.
Has anyone tried either of these and how successful were you? Are these my only options or is there something I may have overlooked?
Hi :) I think ARP poisoning and so on is not so easy to drop in.. ;) but you could start by trying one of the most famous network packets analyzer: Wireshark. Networking is very far to be easy.. :P but Wireshark will help you a lot and, btw, supports also libcap. Hope that helps :)
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I was reading that in order to capture traffic for more than just my machine I need to put the nic into promiscuous mode. By default the nic seems to filter out the packets which are not meant for it.
My Question is : How come my nic even receive traffic that is not intended for it? Isn't my router supposed to route packets only to the computer for which it is meant?
Sorry - newbie here and this may be an absolute down votable question that I am asking.
I have heard that in case of wireless networks, the traffic takes multiple paths and the NIC combines these signals to form the original signal. So when a NIC sends something to the gateway it will send multiple signals and some if not all may even be captured by your packet sniffer.
Monitor mode also works like this
The short answer: It depends. :)
Wireshark Wiki: Ethernet capture setup should be of help to get you started.
I know, how to write a C# application that works through a local network.
I mean I know, how to make my client-side application access my server-side application in a single local network.
But I wonder: How do such apps, as Skype, TeamViewer, and many other connect via global network?
I apologise, if this question is simple or obvious, but I couldn't find any information about this stuff.
Please, help me, I'll be very grateful. Any information is accepted - articles, plain info, books,and so on...
Question is very wide and I try to do short overview.
Following major difference between LAN (Local Area Network) and WAN (Wide Area Network):
Network quality:
LAN is more or less stable, WAN can be with network issues like:
Packet loss (you need use loss-tolerant transport like TCP or UDP with retransmits or packet loss concealment)
Packet jitter (interpacket intervals may differ a lot from sending part). Most common thing is packets bursts.
Packet reordering
Packet duplication
Network connectivity
WAN is less stable than LAN. So you need properly handle all things like:
Connection stale
Connection loss
Errors in the middle of the connection (if you use UDP for example)
Addresses:
In WAN you deal with different network equipment between client and server (or peers in case of peer-to-peer communication). You need to take in account:
NATs - most of the clients are behind NAT and you need to pass them through. According technics are called "NAT traversal"
Firewalls - may ISP has own rules what client can do or can't. So if you do something specific like custom transport protocol you may bump into ISP firewalls.
Routing - especially multicast and broadcast communication. In common case multicast is not possible to route. Broadcasts are never routed. So you need to avail this type of communication if you want to use WAN.
May be I forgot something. But these points are major. You can read many articles about any of them.
I've been trying to find a tool for monitoring my home network. Before I go into the details, I've looked at a ton of different software and they're either an overkill or don't have what I'm looking for. Hopefully the community can help me with some advice.
My network is quite small. It consists of a modem connected to a D-Link DI-524 router. To this router I have a number of computers hooked up wirelessly.
What I'm looking for is a lightweight tool for monitoring my traffic. The ideal tool would have a GUI that shows an icon of the router, and icons of all devices connected to the router with a bandwidth indicator on the lines connecting the nodes. That's pretty much it.
I'm not sure if my router has SNMP. This might be a dealbreaker since many of the cheaper routers don't. I've also read somewhere that many routers can be monitored over UDP.
Found tnv after quick googling.
tnv (The Network Visualizer or
Time-based Network Visualizer) depicts
network traffic by visualizing packets
and links between local and remote
hosts.
Here is a list of good tools to monitor network activity.
Looks like MRTG was the best tool to use
I have also been pleased with the Serial and USB software provided by HHD Software. I've never used their Network version, but if its as good as the USB and Serial, its probably pretty good. Here is the free trial version.
you can use CACTI and Mikrotik DUDE.
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