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Thread: Ettercap With ARP Poisoning

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    Senior Member micole's Avatar
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    Jan 2010
    Charleston, SC

    Post Ettercap With ARP Poisoning

    Hey guys. I'm in a new ethical hacking class for my college and coming up with Exercises for the class and decided to post them on here whenever I come up with new ones. Some of the wording would be awkward because I'm just copying it over from my papers so I might refer to you as a student or "us" or "we". I also try to explain to the best of my knowledge what is going on. (I'm sure other people could add to what I already have) If I ever post anything that's wrong let me know so I can edit it.

    Assuming you have a clean install of BT4 with no edits:


    Ettercap is a tool for network protocol analysis and security auditing. It has the ability to intercept traffic on a network, capture passwords, and conduct active eavesdropping against common protocols.

    For this exercise I will be using ARP Poisoning to sniff the LAN for passwords that use SSL (Hotmail, Gmail, Etc.)


    “Address Resolution Protocol”: As defined by Wikipedia: ARP is a computer networking protocol for determining a network host's link layer or hardware address when only its Internet Layer (IP) or Network Layer address is known. This function is critical in local area networking as well as for routing internetworking traffic across gateways (routers) based on IP addresses when the next-hop router must be determined.

    So in normal terms ARP is the way that we get a MAC address of a Host or Node from the IP address.

    ARP Spoofing:

    This is the technique we will use to attack a wired or a wireless network. ARP Spoofing allows the attacker to sniff data frames from the LAN, then gives you the ability to modify the traffic (good for redirecting to your own computer to download an exploit to victim), or stop the traffic from entering the network, or a specific computer (good for local DOS Attacks on a Local Area Network).

    The idea behind the attack is to send a fake (AKA “Spoofed”) ARP message to the LAN. Any traffic on the network meant for that IP address that you attacked (whole network if you want) will be sent to the attacker. The attacker (you) can choose to forward the traffic to the actual gateway (Passive Sniffing) or modify the data before forwarding it (Man in the Middle).

    How we will do it for this exercise:

    Edit a file:

    We first have to edit one file (Don’t worry, we just have to delete two # signs to “uncomment” them).

    The file we will be editing is called etter.conf and it can be found under the etc folder. (Full Path = /etc/etter.conf)

    We need to change the part under the “redir_command_on/off” section. It is under the Linux sub heading.


    The Linux subsection will look like this when done:

    #     Linux 
    # if you use ipchains:
       #redir_command_on = "ipchains -A input -i %iface -p tcp -s 0/0 -d 0/0 %port -j REDIRECT %rport"
       #redir_command_off = "ipchains -D input -i %iface -p tcp -s 0/0 -d 0/0 %port -j REDIRECT %rport"
    # if you use iptables:
       redir_command_on = "iptables -t nat -A PREROUTING -i %iface -p tcp --dport %port -j REDIRECT --to-port %rport"
       redir_command_off = "iptables -t nat -D PREROUTING -i %iface -p tcp --dport %port -j REDIRECT --to-port %rport"

    Notice how there are no Pound (#) signs in front of the last two lines.

    Run Ettercap:

    Now we can start Ettercap-GTK (This is a pretty version of the shell program, it gives us a nice GUI to play with). Ettercap-GTK can be found under: Menu -> Backtrack -> Privilege Escalation -> Spoofing -> Ettercap-GTK

    Setting up Sniffing:

    Sniff -> Unified Sniffing

    Eth0 -> OK ………………………..(This runs Sniffing on your first Ethernet card)

    Hosts -> Scan for hosts ………… (Scans the network for targets)

    Hosts -> Hosts List ………………….(Opens your hosts list

    Now, you have all the computers on the network on the host list. If you want to only scan one computer (its better and quicker for us to just do the one) then click on the default gateway first, and click the target 1 button.

    After you do the default gateway, then click your computer you are attacking and make it “Target 2” by selecting it and clicking the “target 2” button.

    After setting up the sniffing:

    Mitm -> ARP poisoning -> Select “Sniff remote connections” Hit OK

    Start -> Start Sniffing

    Your done! Now you are sniffing the computer for passwords onto certain websites that use SSL for their security. When you are done go to: Start -> Stop Sniffing, and then go to Mitm -> Stop mitm attack(s)


    When you run this, the SSL certificates on some websites will not be valid, so the user has to constantly hit yes for the attack to run successfully. For most users this won’t be a problem seeing as how they “Trust” the site usually and will hit yes.

    Protect yourself:

    Don’t hit yes for all of the SSL certificates when you know the website should be up to date because you know your being attacked.

    Link to a good Detection and Prevention paper from San Jose Stat University:
    Last edited by micole; 03-10-2010 at 06:37 AM. Reason: "protect yourself" changes

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