Warning: DO NOT use this to damage Cisco systems, or gain unauthorized access to systems. This tutorial is just something to use for educational purposes. Only use this information in a legal way (the hacker wargames for instance), and do not damage or destroy anything. This is a step-by-step guide on how a series of proven cisco exploits can be used to gain access. If you get caught breaking into a cisco router, or screw the system up, you can interrupt hundreds of internet clients, and cost thousands of dollars, so only use this when you are allowed!! Using this the wrong way will get you into a lot of trouble.

Section 1: Why hack a cisco router?

You probably are wondering.. why hack into a cisco router?

The reason being is that they are useful when it comes to breaking into other systems...

Cisco routers are very fast, some with 18 T1 connections on one system, and they are very flexible and can be usedin DoS attacks or to hack other systems since most of them run telnet.

They also have thousands of packets going through them at any one time, which can be captured and decoded... A lot of cisco routers are also trusted systems, and will let you have a certain amount of access to other computers on it's network.

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Section 2: finding a cisco router

Finding a cisco router is a fairly easy task, almost every ISP will route through at least one cisco router. The
easiest way to find a cisco router is to run a traceroute from dos (type "tracert" and then the IP address of
anyone's computer), you can trace pretty much anyone because the trace will show all of the computer systems between your computer and their computer. One of these systems will probably have the name "cisco" in it's name. If you find one like this, copy down it's IP address.

Now you have the location of a cisco router, but it may have a firewall protecting it, so you should see if it's
being blocked by pinging it a couple times, if you get the ping returned to you, it might not be blocked. Another way is to try to access some of the cisco router's ports, you can do this simply by using telnet, and opening a connection to the router on port 23.. If it asks for a password, but no username, you are at the router, but if it wants a username aswell, you are probably at a firewall.

Try to find a router without a firewall, since this tutorial is on the routers and not how to get past the
firewalls. Once you're sure you have found a good system, you should find a proxy server which will allow you to use port 23, this way your IP will not be logged by the router.

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Section 3: how to break into a cisco router

Cisco routers running v4.1 software (which currently is most of them) will be easily disabled. You simply connect to the router on port 23 through your proxy server, and enter a HUGE password string, something like;

10293847465qpwoeirutyalskdjfhgzmxncbv019dsk1029384 7465qpwoeirutyalskdjfhgzmxncbv019dsk10293847465qpw oeirutyalskdjfhgzmxncbv019dsk10293847465qpwoeiruty alskdjfhgzmxncbv019dsk10293847465qpwoeirutyalskdjf hgzmxncbv019dsk10293847465qpwoeirutyalskdjfhgzmxnc bv019dsk10293847465qpwoeirutyalskdjfhgzmxncbv019ds k10293847465qpwoeirutyalskdjfhgzmxncbv019dsk

Now wait, the cisco system might reboot, in which case you can't hack it because it is offline.. But it will
probably freeze up for a period of 2-10 minutes, which you must use to get in.

If neither happens, then it is not running the vulnerable software, in which case you can try several DoS attacks,like a huge ping. Go to dos and type "ping -l 56550 cisco.router.ip -t", this will do the same trick for you.

While it is frozen, open up another connection to it from some other proxy, and put the password as "admin", the reason for this is because by default, this is the router's password, and while it is temporarily disabled, it will revert to it's default state.

Now that you have logged in, you must acquire the password file! The systems run different software, but most will have a prompt like "htl-textil" or something, now type "?" for a list of commands, you will see a huge list of commands, somewhere in there you will find a transfer command, use that to get the password file of admin (which is the current user) and send it to your own IP address on port 23. But before you do this, set up HyperTerminal to wait for a call from the cisco router. Now once you send the file, HyperTerminal will ask you if you want to accept the file that this machine is sending you, say yes and save it to disk. Logout.

You are now past the hardest part, give yourself a pat on the back and get ready to break that password!

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Section 4: breaking the password

Now that you have acquired the password file, you have to break it so you can access the router again. To do this, you can run a program like John the Ripper or something on the password file, and you may break it.

This is the easiest way, and the way i would recommend. Another way would be to try and decrypt it. For this you will need some decryption software, a lot a patience, and some of the decryption sequences.

Here is a sequence for decrypting a cisco password, you have to compile this in linux:

If you do not have Linux, then the only way to break the password is to run a dictionary or brute-force attack on the file with John the Ripper or another password-cracker.

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Section 5: Using the router

To use this wonderful piece of technology, you will have to be able to connect to it, use a proxy if you do not want  your IP logged. Once you have logged in, you'll want to disable the history so no one can look at what you were  doing, type in "terminal history size 0". Now it won't remember anything! Type "?" for a list of all of the router's  commands, and you will be able to use most of them.

These routers usually have telnet, so you can use telnet to connect to other systems, (like unix boxes) and hack into them. It also is equipped with ping and traceroute, which you can use to trace systems or do DoS attacks. You  may also be able to use it to intercept packets, but i do not recommend this, as it will not always work, and may  get you noticed....

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If you don't hack a cisco your first time, don't worry... you probably won't do it the first time, or even the
second. It takes practice and patience. This is just to show you how... And make sure you are going after something that is LEGAL.

Thanks...