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How Should One Respond to a Network Break In?
Jety asks: "I am the sole IT support for a medium sized residential real estate office. It has a network of one main server, 10 office workstations, and another 40 or so agent's personal computers. I discovered via logs that recently someone made about 50 remote login attempts to the server, guessing at passwords, but it would appear that they were not able to gain access. They did, however, leave an IP address in the logs. It turns out to be an Exchange server for another business in the same city.
What is an appropriate response to this sort of failed break-in attempt? How seriously should one react? How should it be presented to management, and should you encourage them to over or under react? Should the other business, whose server was used to launch the attack, be informed? Should you try to surveil them first to learn about who is doing their tech work? With what tone should they be approached and/or accused? What would a suitable response from that company entail?"
Document everything in writing, discuss the situation with your superiors, and seriously consider initiating some form of legal action. If you are the first to get litigious, you stand a better chance of having the situation resolved in your favor. Unfortunate, but true.
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~ |rip/\/\aster /\/\onkey
You shouldn't start out accusatorily, because it's most likely that they're not the ones attempting the breakin. It's more likely that their box has been hijacked and is being used as a proxy to launch attacks against your computer for someone else.
After all, who uses an exchange server as their terminal to log in to other computers? If it was one of the desktops, then it would make sense that they were attacking.
Remember, there were no nuclear weapons before women were allowed to vote.
You try contacting abuse@ the other company.
If that fails, you call them up and ask for their tech-lead.
You already have your logfiles, and reasonably secured server.
What you can gain here is a partnership - or at least an exchange of favors every now and then - between your company and the remote one.
That said, if the other company isn't responsive, you firewall them to hell and get on with your daily work.
You'll want to give management a brief notice about what's happening before you do this, obviously.
After you've talked to abuse@, you tell management what happened.
Now is the time to see over your authentication schemes. Are your users logging in over SSH? With passwords instead of keys? (Hint: keys are nicer).
After this is said and done, you paypal me $90 for doing your job.
Cheers!
Start off by blocking remote logins (ssh?) from anywhere except where you want to allow people to log in from. Second, I would send a polite, email to their tech contact, or if you can't find that, regular post mail to the company. Don't overreact. Their are a lot of ssh worms out there. I have one machine where I watch for these kinds of things. I see at least 3 or 4 worms hitting my box a day.
I always celebrate. Oh wait, you mean as the victim? Hrm..
Frankly I'm a lot more afraid of a successful breakin that I don't discover than heaps of unsuccessful attempts that I do.
Essentially everyone who attempts to hit my ftp server with anonymous is trying to break in - the address is only known to a few people who have accounts and I can see from the logs that the other attempts are just scripted tries.
Similarly, I'm see several attempts every day to log into my machines via ssh (where an attempt may involve from a dozen to hundreds of tries to log in). Don't even get started on what I see in the http or smtp logs.
I work at a small company, too, and I could pull everyone off their jobs and still not have enough manpower to investigate each attempted breakin, locate and contact the appropriate parties, etc.
As mentioned elsewhere, most of these machines are compromised so you are really spending your time to provide unpaid antivirus support for the other party's machine. You have to pick your battles.
Depending on my workload and the probability of a positive result I'll contact someone as a courtesy. Generally my criteria is that I am able to make telephone contact with a person responsible for the machine relatively quickly.
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"You are not remembered for doing what is expected of you." - Atul Chitnis
It might be not even them due to spoofing, but most likely, it is unauthorized use of their machine.
How would you go about brute forcing a server using IP spoofing? With IP spoofing, you don't get the packets to return to you, they get returned to the server, then dropped. No complete TCP connection can be made.
Therefore, SSH would never get the packet to begin with, and even if it did, and got your full packet, it wouldn't send the "success" or "failure" to you.
That computer is obviously either compromised (most likely), or being used by authorized personnel to launch this attack (very unlikely).