While poisoning an ARP cache, it is the legitimate user whose reply is received first rather than the attacker's fake reply when a corresponding request is sent. Maybe because the attacker is dependent on the user level program to sniff the request and generate the reply.
As your question was which component my answer is software.
The IP module sends a packet to the ARP module. It looks up the ARP cache to resolve the IP address. If it is present in the cache, it is resolved into its Ethernet address. If the ARP module is not able to find an entry for this IP address in the ARP cache, then it sends an ARP request packet to the Ethernet driver, to resolve the IP address to the Ethernet address.
When an ARP request packet is received by a host: If the IP address to be resolved is for this host, then the ARP module sends an ARP reply packet with its Ethernet MAC address And updates its ARP cache with the source Ethernet MAC address to source IP address mapping present in the ARP request packet. If the entry is already present in the cache, it is overwritten. If it is not present, it is added. If the IP address to be resolved is not for this host, then the ARP module discards the ARP request packet.
As your question was which component my answer is software.
The IP module sends a packet to the ARP module. It looks up the ARP cache to resolve the IP address. If it is present in the cache, it is resolved into its Ethernet address. If the ARP module is not able to find an entry for this IP address in the ARP cache, then it sends an ARP request packet to the Ethernet driver, to resolve the IP address to the Ethernet address.
When an ARP request packet is received by a host: If the IP address to be resolved is for this host, then the ARP module sends an ARP reply packet with its Ethernet MAC address And updates its ARP cache with the source Ethernet MAC address to source IP address mapping present in the ARP request packet. If the entry is already present in the cache, it is overwritten. If it is not present, it is added. If the IP address to be resolved is not for this host, then the ARP module discards the ARP request packet.
Thanks a lot for your comments. Hardware is only like a metal, all logics of its functioning is in the software.
Peter, I really appriciate your little lesson. Thank you so much. It was very interesting to learn smth new for me.
Peter, I've just visited your page and found that it is your special field of knowledge. Your explanations were very valuable for me. Thank you again!
Just to add one thought to this - back to the primary question: the 'legit' ARP Reply behavior is to 1) identify incoming packet as an ARP request, 2) verify whether it is a request for my IP address, 3) if so, send response with my MAC. The ARP spoofer doesn't need step 2. Therefore, one can conclude if you implement this behaviour in hardware, spoofing system will always be faster than 'legit' system?
And for the ARP request you receive, your system modifies its ARP table (learning), so it is a software part as well, am I wrong? As for ARP requests, your system generates it if you don't have the ARP entry in your ARP table. So, again, it would seem an operating system (software) part to do.
Peter is of course right, but the initial question was about ARP poisoning and spoofed vs. legitimate user response. So it's not about routers, but PCs. That's why I issued those thoughts, because I am not an expert on OS behavior.
It is a nice question and I asked myself that very recently.
I think that, besides very specific applications, ARP is generally implemented in software. Simple ARP can be made really dumb (storage could be a problem), but then you have useful scenarios where you need a punch above of functionality (like proxy-ARP) and that may need a bit more intelligence than the typical COTS hardware offers.
Then, integrated switches (speaking of electronic chips, like those from Marvell or Broadcom) nowadays claim to support a lot of functions implemented on dumb-clockwork-sand (nice expression!). One example is LACP that most (mid range) routers claim to support. Trouble is they lack a minimally smart algorithm for distribution of flows because it is all handled in hw in quite a dumb way. I have currently an issue with a L2 switch because of that. And then you cannot blame the vendor because the actual algorithm is not under IEEE scope. Result is LACP is completely useless for load balancing.
So not all is white and black, I guess, but whenever something needs a bit more intelligence I instantly assume it is in the kernel.
of couse by software! Arp is a protocol enclosed in MAC.Mac is also a software.but Mac is implemented in the way of hardware which fixed the Mac program code. ARP program code is not fixed in a hardware,so ARP Request/Replies is generated by Software which is usually supported by kernel .
ARP is a protocol enclosed in MAC. Hence it is certainly considered as software irrespective of where it is implemented? And software means it gets support from kernel to run.
ARP is implemented in RAM of PC under the support of kernel.In fact ARP program is usually included in a operating system (MS windows or Unix /linux etc.)
There are two problems:
- of course ARP is implemented in OS (in PCs at least). You can build network without TCP/IP stack (f.e. IPX/SPX or NetBEUI) and your NIC will not "understand" ARP-request nor reply on it, if you send it to the NIC.
- But in APR-spoofing attack most of the OSes "trusts" the LAST (not the first) ARP-reply (in some cases, the OS adds MAC/IP pair to their ARP-table, even if they did not send any ARP-request earlier !) so it is profitable for the attacker to not send ARP-reply too quick.
Windows 7 and later versions of Windows all support ARP offload (see http://msdn.microsoft.com/en-us/library/windows/hardware/ff570391(v=vs.85).aspx and http://download.microsoft.com/download/D/1/D/D1DD7745-426B-4CC3-A269-ABBBE427C0EF/NET-T714_DDC08.pptx), where ARP and IPv6 Neighbor Discovery responses are generated by the hardware. This allows the system to stay in a low power state until actual communication is needed with the machine. Many routers or apps periodically ARP to see if hosts are still there even if there is no actual data traffic for the host. Hence this hardware support for ARP can provide a significant power savings. Such hardware support for ARP and ND has been available in many PC NICs for years and indeed it's been a logo requirement since 2010.
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